This is my updated instructable on how i used a standard pc power supply for my XBOX 360. This is not my original idea, I saw a few different ways to do this on the internet but this is what I did and it worked for me. This is an easy way to avoid speanding money on a new or 3rd party 360 power brick and be able to power some pc fans for my new cooling mod.
I warn anyone who decides to use this instructable, if your power supply doesn't meet the minimum power requirements YOU WILL KILL YOUR XBOX !!!!!!
Step 1: Power Requirements
Before you start cuting wires and buying things your going to want to know how much power your 360 needs. Turn your Xbox360 so you can see the back and look at the left side(from back). Right above the power plug is what you are looking for. My xbox360 elite uses 16.5 amps on the 12 volt rail and 1 amp on the 5 volt. The number you want to worry about is the 12 volt rail, this is what you will look for when choosing a powersupply. The supply i used supplies 25A on the 5V and 19A on the 12V.
Once you have found the power supply you will use, the next step is to connect your new power supply to your xbox360.