It could be a few things.
Have a look inside the case and see if the CPU fan is running. Maybe check all the fans you can see.
It sounds very like a problem I had with this PC a few months ago where we would get the BSoD (Blue Screen of Death) and a memory dump at about 5 to 10 minute intervals.
Took the side off the tower unit (which was sitting on a carpet) and OMG! Dust and fluff everywhere. Hoovered it all out and also took the CPU fan off, cleaned all the accumulated gunk out from between the heatsink fins and ..... hey presto - no more overheating and BSoDs ... Bingo!
Before I came to that concluson though, I managed to download a monitoring utility from the web site of the motherboard manufacturer that gave me a graphocal and numerical representation of the MB & CPU temps, plus an indication of all the fan speeds and supply voltages along with a set of guide values. Very frightening as it all went into meltdown. At least it nailed the problem.
I also thought I had a virus but couldn't trace it. Just heatstroke.
Hope that helps
ST