PC Power Supply is just one of the links you can find with google.
I'll try and help with several points here tho...
1. If you have to ask, then odds are that you should get help performing this sort of mod.
2. See those big capacitors inside? Take it as gospel that because of them you need to wait 10-15 mins before touching the PS after removing power.
3. Most power supplies are overrated. Unless you paid a lot of money when it was new (relatively) you can find that 10-15% under the printed rating might be closer.
4. a large percentage of AT/ATX power supplies require a 10-20% load across the 5V line to get the proper voltage on the 12V rail. (Otherwise you'll end up with a PS running at 11.7V for example)
5. Make sure you use decent cable. If you reuse the old cable remember that they have been bent and twisted a bit from PC usage. If you want to get 5amps+ through each wire you're on you own when the meltdown hits.
cheers