| 1) Like the above poster said, clean the dust.2) Make sure the fans are working (*especially* the fan on the power supply)
 3) Run MemTest86 for a while.  This will tell you if it's bad ram.
 4) If the problem still occurs, it is most likely a bad power supply.  Do *not* replace it with a cheapo though, get Fortron, Antec, OCZ, or Zalman (there's a couple of others..).  A bad PSU can fry the rest of your components or even worse - start a house fire.
 
 This happened to my mother's computer (Running win98, heh).  The fan on her PSU burnt out and 4 months later the PSU burped up a cloud of dust and died.  Even if you clean out the case the PSU is probably filled with dust.. (I wouldn't recommend taking it apart though)
 |