About 10 months after I built my system I started getting some stablity issues. I used a simple PSU tester(one of the LED ones) to test my psu and it didnt show power on the -5v rail. I checked the tester out on a couple of psu's that tested good. So I RMA'd my psu and got a new one and installed it and still had the same problems. I then took the psu back out and tested it again and it still didnt show power on the -5v rail. I RMA'd the psu again and when I got the second replacement I tested it right out of the box and this too tested bad. This may be irrelivent to my main question, but while waiting on the second replacement I checked out the rest of my hardware and found my CPU was bad which I relplaced. I know have the system running again but with a different lower quality PSU. The PSU in question is a Kingwin ABT-600MA1S. My question is, am I missing something? Could the PSU actually be good even though my tester doesnt show power on the -5v rail? Or have I just been a victim of bad luck. Also what exactly is the -5v rail used for? The PSU doesnt have this rail listed on the sticker that is on its side and most PSU's that I have seen have -5V on the sticker along with its amperage.