Originally Posted by copelandtml
Intel Pentium D 820
2.8 GHz processor
512 MB ram
232 GB harddrive
Get another stick of 512 memory & your system will run loads better.
But yeah, did you replace the thermal compound with new one? or did it already have some applied to the new fan/heatsink?
Have you checked your graphic's card? That to can produce heat if the fan has failed & can cause the pc to just shut off.
But, the heat must come from somewhere, best bet is to run it until it turns itself off with the side panel off & when it turns off, quickly pop your hand in but dont touch anything & see if you can feel where its mostly hot & that should give a good indication.
Other than that, i can only think of a under powered cpu fan/heatsink.