"AT/ATX power supply replacement guide
No hardware guide would be considered complete without an article dealing
with the replacement of the computer's power supply. It's a simple procedure
but hey, if all the resources were for more advanced users, few users would
be very advanced."
FULL STORY @ TECHDUNGEON (http://www.techdungeon.com/hardware/guides/2000/replacingat-atx/index.shtml)