jdmac:
Try this.
Easily Convert an ATX Power Supply to a Lab Power Supply
jdmac
Mims, Fl
Yeah, but this is giving exactly what you should avoid: no current limitation, and with this you will produce (for sure) a lot of magic blue smoke 
Problem is that the PSU is able to deliver huge amount of current (> 30A on 5V). Imagine you have a short on your test circuit....... Better is to limit the current, or at least integrate fuses (but this was too expensive for me, considering the number of shortages I produce per day in average ]
).