* Please note: I have a number of product links and prices in this article which may change at any time. I'll try to keep it updated, but don't expect products to be available or prices to be the same.
Minimally, here are the 9 hardware components you will need to build your media pc:
- Case
- Power supply (many cases come with the power supply)
- Motherboard
- Processor
- RAM
- Hard Drive
- DVD Drive
- TV Tuner
- Keyboard & Mouse
Other hardware components you will likely want to add to your media center pc are:
- Card Reader
- Remote Control
- Router
- Wireless Adapter
Don't worry, I'll explain each of these components and describe what I purchased and why.
Before I begin, let me just say that I recommend buying all your parts at Newegg.com! They have the best deals I've seen, awesome customer support and return policies, a very user-friendly website, huge selection, and they have tons of information and customer reviews on their product pages.
1. Case

For me, this one was a little tricky. We just bought a new entertainment center only to learn that our VCR/DVD combo was too wide to fit in it. Our entertainment center has 3 colums of shelves. Each column is about 15 inches wide. To add to the complexity, the depth is only 14 inches. I found that most of the media center cases I was looking at would not fit - especially the cheaper models I was looking at.
I did find one though. I selected this model. It wasn't listed with the other HTPC / Media Center cases. I did a search in computer cases for a case with a power supply and type of MicroATX slim case. There is no way that I know of to search by dimensions, so you'll just have to check the specifications on the product page. You can see the dimensions on the page here:

2. Power Supply
As I mentioned above, I searched for a case that came with a power supply. For me, this just makes it a little easier and often cheaper. One thing you'll have to keep in mind is whether your power supply will be sufficient for the components you are putting in. If it is not, you may end up damaging some of your components. The case above comes with a 300 W power supply that you can also see in the screenshot. Newegg has a power supply calculator you can use to determine how much power you need. Doing a quick run of the calculator suggestes 338 Watts. I'm still debating on whether or not to buy a replacement. I can order a 380W power supply for $12.99 - not a budget killer. I'll probably stick with the 300 for now, and if I find any problems I'll upgrade ASAP.
If your power supply is not sufficient or the case you selected does not have a power supply, run the calculator to get an idea of what you need. If you are concerned, error on the side of getting more power than you need.
Make sure you get the right size. If you have a MicroATX case, get a MicroATX sized PSU.
Also, just a tip if you are buying a power supply, you want this computer to be quiet. User reviews will often tell you whether the fans are noisy or quite. I built my main computer to be as quiet as possible - and it was until I bought a video card to support dual LCD monitors. My video card sounds like a jet engine! I didn't really take the time to check on that unfortunately.
3. Motherboard

I suppose the most important thing to consider when buying a motherboard is whether or not it will fit in your case! Notice that I searched for a MicroATX case. That means that I want a MicroATX sized motherboard to go in it.
Other things to consider are what type of processor you prefer to use (AMD vs Intel), what kind of connectors it has, whether it has onboard audio and video (most do), etc. If you know this stuff it will help in your search.
So here is the path I went. I first priced AMD and Intel processors. I basically just wanted something with a dual core. You don't need this, it's just a personal preference. If I had gone with a single core processor, I likely would not even have to worry about upgrading my power supply.
I found compatible AMD processors and motherboards and added them to my cart. I noticed that the AMD motherboard / processor combo was significantly cheaper than the Intel combo. This is generally the case. I have been running on AMD the past six years or so and have absolutely not complaints.
I also wanted to find a motherboard that had and HDMI output so it could plug right into an HDTV.
I wanted at least one IEEE 1394 connector so I could use FireWire to plug in my video camera (or I could just use USB, but I've heard FireWire is better for that stuff).
My search results found a few options. Some people have stong opinions on brands of motherboards. A friend of mine will only buy ASUS for example. I opted to use Gigabyte for my personal computer based on glowing reviews. I'm generally open to any brand until it gives me problems, but with motherboard, I must admit I tend to gravitate towards recommended brands whether conciously or sub-consciously, I don't know.
I opted for this ASUS model. Really the two choices I was considered ironically enough were ASUS and Gigabyte. They had relatively the same specs and same price. I found this open box deal on ASUS though that saved me about $20 so that was the ultimate tipping point.
* UPDATE: I guess I didn't realize this, but the open box deal didn't come will all the wires and manual, etc that the retail box will. Lucky for me I had an extra SATA and IDE cable that I could use that was left over from a previous built. I downloaded the manual from the manufacturer's website. Unless you really know what you're doing, I suggest making your life easier by avoiding open box.
4. Processor

As I mentioned above, my CPU selection pretty much went hand-in-hand with my motherboard selection. Processors are made by Intel or AMD. AMD as I mentioned are generally cheaper for similar porformance models. Motherboard are either made to support an Intel model or an AMD model.
I chose this model because it was the cheapest dual core processor available at $35.99 with free shipping. Plus it had glowing 5 egg reviews so I was pretty confident I would be pleased with it.
To match up your processor with your motherboard, check the specifications and make sure your motherboard will support your processor selection. See screenshots below:


One thing to note, you'll just need to make sure that you processor speed is supported by the other components you select. For example, check out the specs on the TV Tuner card I selected below.
* UPDATE: I didn't realize that with OEM you need supply your own heatsink and fan. I had to order this after the fact. I suggest buying the retain box that comes with a heatsink and fan.
5. RAM

Your decision for the amount of RAM or Memory you choose will greatly affect you perfomance. I stongly suggest getting 2 GB or more if you are going to run Vista. I'm personally using 4 GB on my main computer and sometimes wish I had more. But I run a lot of programs at the same time. With my media center, 2 GB should be plenty.
Again, check your motherbaord specifications for the type of memory you need to get. My motherboard supports DDR2 1066 memory, so that is what I searched for. I chose this memory by Kingston. It had a low price of $23.99 and great reviews.
I opted to get a single memory chip rather than 2 x 1GB chips thinking that if I needed to upgrade, I would just come back and buy the same chip to double my memory. My motherboard supports 4 chips and up to 8GB or RAM, so ultimately it most likely doesn't matter.
6. Hard Drive

As far as hard drive's go, the more storage you can get, the better!
Sadly, I chose to skimp in this area as I was striving to stick within a $500 budget. Still, I got this 320 MB Hitachi hard drive. That saved me $50 off the 1 TB hard drive I really wanted to get. Ultimately, the more storage you have, the more shows and movies you can record on your DVR and the more DVDs you can back up to your hard disk.
Oh well, there is another bay available in my case if it comes to the point where I really feel I need that extra storage. Or there is always the option of getting an external hard drive that can plug into the many USB ports available on my board.
If I do get a second hard drive, I will definitely need to upgrade my power supply.
7. DVD Drive

At first, I thought this might be optional, but really it is not. Even if you don't plan to use this as your DVD player, you will still need this to install your operating system and other software you may have on disk, so just get it.
You can turn your PC into a Blu-ray player with a Blu-ray drive for as low as $90. You could even upgrade it to a Blu-ray burner for as low as $200.
Still both were out of my price range. I opted to get this DVD±R DVD Burner which was only $21.99 with free shipping.
If you don't think you'll ever need to burn any DVDs or CDs, feel free to just get a DVD-ROM drive and save yourself $3 - but hey, it's only $3, so disreguard that advice because at some point, you will want to burn something!
8. TV Tuner

So, where I skimped on the hard drive, I did not skimp on the tv tuner card. This is more important to me than storage.
I really wanted a dual tuner card. This would allow me to watch a show while one is being recorded, or record two shows at the same time. Another option is to buy two TV tuner cards, but then we are taking up some precious PCI space right?
So I decided to go with this Hauppauge model. I'm going to go out on a limb and say that Hauppauge is probably the most popular TV tuner card manufacturer.
Here is what I like about the card I selected:
- Dual tuners
- NTSC/ATSC/QAM on each tuner, with only a single connection
- Dual MPEG2 Hardware accelerated controllers for SD content
- FM Tuner to listen to the radio
- Two IR blasters (for controlling two cable boxes)
- Optional half height/L-P bracket - which will be needed with my small case!
You should be aware of the system requirements on this one:
Processor requirements: 2.2 GHz P4 or equivalent (minimum) required for displaying ATSC high definition TV on your PC screen
Microsoft Windows Vista Premium or Ultimate with Media Center or Windows XP Media Center Edition. Windows XP is supported with Hauppauge's WinTV v6 application.
Available PCIe X1 or X8 slot
Graphics with 64 MB memory (or greater)
Sound card
CD reader for software installation
Notice that PCIx X1 or X8 slot? Yes, my motherboard has this. The graphics with 64 MB memory is the only question I had on this. My motherboard on the onboard graphics, but the specifications listed only say "ATI Radeon HD 3200". After doing a quick Google search on that it appears that it has 512 GB of memory, which seems to be pretty standard, so again, I should be fine.
9. Keyboard & Mouse

This should be obvious, and I hesitate even mentioning it, but you are really going to want a wireless keyboard and mouse!
We don't really have a coffee table or somewhere to use your standard type mouse, so I wanted to find a keyboard with a trackball in it. Simple enough, Newegg has a search for that too!
I didn't go with the cheapest model this time becaue it had bad reviews - mostly that it kept losing its connection. While I'm not terribly concerned about keyboard quality (mainly because I will mostly be using a remote control), I don't want to buy a piece of junk either. I opted for this model which seemed pretty nice.
Notice that it comes with a remote control too. This is pretty cool. Still, I read some complaints on the reviews about the remote which prompted me to order a different one which Newegg was offering a great combo discount on with the case I orderd. You will find this a lot with Newegg. After adding an item to your cart, it will often let you know about discounts you can get when you order other items with the one you just added to your cart.
Optional Components
10. Card Reader

I'll admit, this is just one thing I forgot to fit into my budget! No worries though, you can find this for $10 on Newegg.
Just a few things to note, you should make sure you get the size that will fit your case. I prefer the ones that fit the 3.5" external drive bay. These were generally for floppy disks, but who uses those anymore?
Also, make sure the type of connector that you need is available internally on your motherboard.
One last tip, I prefer to get one that also has a USB port in it. You can never have too many USB ports!
So after a quick search, if I were to buy one now, it would likely be this 68-in-1 model for $13.99 with free shipping.
11. Remote Control

I find that Window Media Center remote controls generally get good reviews overall. Because the remote that comes with my keyboard is not an MCE remote, I decided to get one.
The main decision to do so, what that this remote was offered as a combo discount on nearly everything I put in my card - so what the heck, why not?
This is an infrafred remote, which means I'll have to use the little receiver box. There may be other options such as radio frequency (RF), Wi-Fi, or Bluetooth that you may want to consider.
12. Router

OK, this technically isn't part of your computer, but if you don't have a router, you'll likely want one.
I recently purchased this dual band wireless n gigabit router. My previous router was a wireless g (up to 54Mbps) and the LAN/WAN ports only supported up to 100Mbps. This new router will support up to 300Mbps wireless and 1000Mbsp wired.
I plan to have this media pc wired directly to the router for faster speeds. But in the future I will probably put a media center extender in our master bedroom and so I will be using the wireless for that.
13. Wireless Adapter

If you are going to use a wireless router and connect to your media center pc that way, you will likey need a wireless adapter. Be sure to get one that supports the speed you want.
For example, if you are getting the Wireless N router like the one above, you will need a wireless adapter that supports N speeds to get the maximum benefits. These generally start around $20 and go up from there.
There are a few things to keep in mind here also. You can get on with a USB connector, or one that plugs into a PCI slot. I would choose one that uses a PCI slot just as a personal preference - it looks cleaner to me. But, for the case I have, it would need to be a low-profile bracket to fit. I didn't really see any low profile brackets, so you might be better off just getting a USB type.
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Well, that's it for the hardware - unless you want to look at game controllers and other neat stuff. I'll leave that up to you.
My hardware is on its way. Here is a screenshot of the items I ordered, showing that everything shipped is under $500. (Keep in mind, I may need to go back and order a better power supply and card reader, also, this did not include my router.)

Once my hardward arrives, I'll move on to Step 2: Building the Machine.