Those PSUs should have been good enough. I'm starting to think you've a software problem on your hands.
Did you have two hard disks on hand with Windows 7? Did you install the same programs on both of them?
If that's not the case, the only option left is a malfunctioning motherboard (that I can think of, at least).
December 17, 2009 7:56:49 PM
I don't think the symptoms match a software problem! The fact that id can freeze before I even log-on makes me suspicios for a start. Also, there is nothing I can think of non-standard (i.e. not part of Win7) on there yet. I only reinstalled Win7 the other week, hoping that would cure it. Finally I tried another fresh install on a different disk and that froze too.
I'm going to run the memory tests again (overnight) and think about buying a new motherboard in the morning:-(
Would be good to know if there is anything else to rule out or of any conclusive tests I could try first!