your computer has its own way of saving its life. if it senses that it is too hot, it will solve the situation by shutting itself off. the P4 Prescotts are notorius for running hotter because of the 90nm technology used in their design. but, from your mention of Intel 530, it is obvious that you have one of the new LGA775 cpus. they also are notorius for running hot because of the same reason (90nm technology). download the Everest utility I mentioned, and pay attention to the temps given.

from what I have read, said processors do run hot, but if properly installed there should not be a heat issue. but if imporoperly installed (sub-standard heatsink, no thermal paste, etc) there have indeed been plenty of problems. and take a look inside your box to see if there is a problem with the heatsink/fan combination for the cpu