What model and brand power box in your machine?  The K7S5A's legendary for 
finickiness.  I had one in my parents' system (formerly mine).  With Deer and 
@power 300 watt boxes, crash city at the rated speed of the CPU (1666MHz).  With 
a Sparkle 300, perfect.  The Sparkle probably massed 2x the other brands.  I 
paid 55 or so for mine af Fry's back when they sold 'em, now you can find them 
online for like 30