Step 1: Why Do This?
Step 2: Buy a Broken Laptop.
When looking for a laptop, keep in mind that whether you're using XP Media Center, Windows 7 Media Center, MythTV or any of the other popular HTPC options, the more horsepower the better. Luckily there are a lot of people selling laptops on auction sites that have no screen, keyboard, power adapter. In other words, they're complete basket cases. For our purposes though, this is perfect.
Ideally you'll want to buy the fastest computer you can for the least amount of money. I picked up a Pentium Core2 Duo 1.6Ghz laptop with 1GB of RAM (No hard drive) for about $50. To get this laptop back into the shape it would need to be in to be a laptop again would have been very expensive as it needed a battery, hard drive, screen, keyboard, and the onboard sound chip was dead. That was all okay though, we only need the mainboard, RAM and Hard Drive. EBay is a great resource for laptops that have been dropped or kicked or dropkicked, so head over there to see what you can find.
Remember though, some of these laptops are too far gone even to use for this project. Make sure you find one that powers up and shows some signs of life. If not, make sure the seller offers a reasonable return policy.
Step 3: Choose a Housing
If you want to go the more funky route, you could get an old VHS (or if you're really lucky, Beta!) VCR and gut it for your HTPC. I thought that an old DVD player would make a good housing also, since there's already a door for the DVD drive, something I left out because I didn't want to cut into the side of the case.
Step 4: Disassemble Your Laptop
Those last two are really important. Regardless of the type of video connection you'll be using, you need to make sure that the housing has adequate room for the plug end of the cable while it's mounted in the case. It's equally important to decide well in advance of breaking out the hot glue gun how you're going to connect this machine to the network. If you have the option of hardwiring the box to the network you're in great shape. All laptops come with at least a 10/100 ethernet connection on-board, they're more reliable, and faster than most wireless connections. Since your laptop probably came with a wireless card you may be tempted to use it. If you go this route you'll need to make sure you have an antenna strategy worked out ahead of time.
Step 5: The Ins and Outs of Wireless Networking
First, laptops have very, very tiny antenna connectors. Most use the U.FL connector (two of them-one primary and one alternate) and have cables snaking throughout the body of the laptop where they end in a printed circuit board antenna up near the screen. This provides better reception when the lid of the laptop is open, but these tiny antennas are very susceptible to interference from nearby electronics, and are specifically tuned to work in that laptop. To get good reception to your HTPC you'll need to extend these connections outside the box where a more traditional antenna can be used. To that end, click this link to find cheap U.FL to SMA or TNC cables. You'll also need a couple of antennas which should be easy to find on eBay.
Secondly, most laptops have the ability to switch the wireless on and off to conserve power. If your laptop has a physical switch you're in luck. If your laptop has a key combination that you hit (or even worse, a single button), you'll have to get creative. For those with the key combination (Fn+F2 on many Dells), there is typically a bios setting that can be enabled for the wireless radio. Turn it on and you're golden. If you have the button, you'll need to extend that button to the outside of the housing to turn your wireless on should it ever turn itself off. And it will. Every time you turn the stupid thing off.
At the time of this writing, I haven't gotten the wireless networking 100% figured out, but the cables are on the way. I'll post pictures once it's all complete.
Step 6: Gut the Tivo, and Use What You Can.
You'll also want to plan how you'll mount the board. It needs to be insulated so as not to short out any of the circuits on the mainboard. I used clear contact paper to line the bottom of the housing before I started doing any drilling, even though the board would be about 1/4" off the bottom of the case.
Once I figured out where everything would go, I laid the mainboard in the case in the exact position it needed to be in. Using a permanent marker, I made dots on the bottom of the case where each mounting screw hole was on the mainboard. I drilled holes slightly smaller than the brass standoffs I would use to keep the mainboard off the bottom of the case, then used an electric drill to screw the standoffs into the holes.
You'll need to understand the wiring pattern for USB ports (Red,White,Green,Black) if you want to reuse the USB ports on the Tivo mainboard. I used a mitre saw to cut through the Tivo's mainboard just behind the mounting holes. This allowed me to use the screw holes in the chassis to secure the board to the case. I then soldered the two USB ports to some cables I had laying around to extend the onboard USB ports to the back. I also soldered a 1/8" stereo headphone cable to the external RCA jacks to connect to the television. The wiring depends entirely on how you want to customize the box, so I'll leave it at that.
Step 7: Mount the Components
Step 8: All the Rest of It...
My use for this machine is as a media center extender for the bedroom. My girlfriend and I can now stream movies from Netflix, catch up on our missed episodes of 30 Rock with Hulu Desktop, or watch any of the television programs recorded on the front room PC from the comfort of the bed. This little computer does a lot more than a typical extender. Another idea I'm toying with is using the onboard modem as an on-screen caller ID. At some point I'll be adding a firewire DVD drive to watch DVD movies.
Step 9: Materials and Prices
Laptop - ~$50 - eBay
Tivo - $10 - Goodwill
USB Sound Card - $5 - eBay
Antenna Cables - $4 - eBay
Antennas - from a box in the garage
Power adapter - from a box in the garage
Remote Control - spare, ~$40 new
Misc. Cables - laying around, but easy to come by
So, I have a lot of excess computer crap laying around. I mean a lot. I would guess that if I didn't have these things and I had to go out and buy everything I used it would have been around $100-120. I also looked long and hard to get the laptop that I ended up with, so some persistence will be helpful. As for the incidentals such as cables and adapters, stick to the auction sites. These seemingly insignificant items are the highest markup items for stores like Best Buy and Radio Shack, and can be purchased MUCH cheaper on eBay.
So, how does it perform?
Why, thank you for asking. The performance is not as good as my main HTPC, but it's good. It choked a bit when I had it at 1920x1080 resolution (1080p), but works great at 1600x900. I think that the computer could benefit from another GB of RAM, 1GB just makes the minimum requirements for Windows 7. Where this box really shines is the noise level. My main HTPC sounds like a DC-9 by comparison. I have to struggle to hear any noise coming from the box when I'm standing right next to it, it's completely inaudible when we're watching it from the other side of the room. I'll leave the heavy lifting to the big box in the living room and this thing can stay on 24/7 without disturbing anyone.
Step 10: Done.