Now that the big black box is no longer available, I thought it would be safe to share a story about my attempt to modify a busted Xbox. What I won't do is provide links to the usual places where one could gain specific information on how to mod an Xbox. Even though Microsoft no longer manufactures the hardware, the hardware itself is protected by copyright and modifying that hardware may be a violation of the DMCA, Digital Millennium Copyright Act. Proceed at your own risk.
A couple of years ago, my hard drive failed on my Xbox. Since it was one of the first off the line, manufactured in Nov. 2001, the warranty had long since expired.
Instead of paying to have my Xbox serviced, I wanted to try to fix it myself. I had read that you could replace the hard drive if you modified your Xbox. I figured that for the cost of the chip and hard drive, I could have an Xbox that had a bigger harddrive and did more than play games. So I ordered a chip which was easy enough and set aside a weekend to install it. I ordered a solderless modchip because I thought it would be the easiest way to go.
I thought wrong. Taking apart the Xbox was easy enough, but installing the chip was a disaster. I couldn't get the system to boot up with chip because I had it sitting on the solderless adapter incorrectly. Then I learned that if the adapter doesn't fit just so, the chip won't boot your system either. Then I figured out it didn't matter because I jacked up the motherboard and it wouldn't boot up at all.
So after some swearing at myself for being so klutzy, I broke down and bought a premodded Xbox from the same folks I bought the chip from and I bought a used one on Ebay to play on Xbox Live. It was highly recommended that I did not use a modded Xbox on Xbox Live even if the modchip was inactive. Then I learned that I didn't need a chip to begin with because there are improved softmods for Xboxes. So I paid extra for a premod for nothing.
All in all, I was happy with my premod and glad to get back on Xbox Live again. However all things being equal, I probably should have sucked it up and sent my broken box in for service to begin with.
The moral of my story, think very carefully about modding your box otherwise you could end up with a $150 paperweight. In my case I spent a couple of hundred dollars above the $100 it would have cost to have it repaired by Microsoft. If you're considering it, do lots and lots of reading. You can google a ton of information about mods.