Try this at your own risk!! Do not try this while the power supply is connected or plugged in.
One of the biggest changes from the old Pentium one computer to the newer personal computers is the internal power supply connector. This was a challenge for me as I wanted a dc-dc power supply for my "AT" based robot but they only readily come in atx fornat.
Unfortunately at the time I needed a converter there was not one made commercially I could find. You could make a sort of Rube/Goldberg pc power supply something like this:
Looks like it might work, so I made a crude cable.
That evolved into the who connection:
Fortunately it worked! Had an ATX PS that it did not work with because of the missing -5v line required by the older motherboards. You can now get the pre-made cables, but if the ATX PS does not have the -5v line (most newer ATX PS boxes do not support -5v) they more than likely will not work.