I have the power supply that came with my Chieftec case, its a no name 420W PS, The best thing I could suggest is to download Memtest86 and test out the memory, You can make a bootable disk for it in order for it to work in XP. See what kind of errors it gives you or doesnt and that will make sure the memory isnt the culprit. Also just as you suspect the PSU might not have enough juice. The Nforce2 chipsets are very finnicky about what RAM will work, at one time Crucial XMS had about a 20% success rate, but the MOBO manufacturers have fixed this thru bios updates. You might want to try the newest bios from EPOX, it is simple to flash it with this board download it extract it to floppy and hit alt-f2 when you 1st get into bios, just make sure you are not overclocked. I would hope that at least 1 of the 3 steps will fix your problem.