Ok, a few days back, my pc turned off and would not turn back on. I thought it was the psu and got a new one. I took my hard drive and put it one my sis pc as master but when it came on, i got a blue screen saying something about hardware failure. When i ran my hard drive as a slave, I was able to access all the stuff on my hard drive. When i put my sis psu on my mobo, the mobo comes on. However, when i put the new psu with her working hard drive on my mobo, it does not want to come on. Can it be that the new psu is not working? How can i test this? That seems as the only logical answer since: -her old psu and my mobo and any hard drive starts but - the new psu or my old psu and my mobo and any hard drive does not start WHATS THE PROBLEM ??????