[Klug-general] P.C. Cut out

[Rich]

Hi All
  I  have a problem with my partner's desktop. It tends to stop working 
at irregular intervals.
  At first I thought that maybe it was a cooling problem as I had to 
remove the heat sink to change the existing drives to hers. I carefully 
cleaned the surfaces of the CPU and heat sink and applied fresh 
compound, but this has not solved it. You can turn the machine on at 
once and it boots up again with no problems. Sometimes it runs for 
hours, sometimes a few minutes.
   I do wonder if the fault was pre-existing when purchased, I only saw 
it running for a few minutes (XP installed).
   Any Ideas appreciated
                                      Rich