The heat the CPU should run

I think that you dont want it over 60 and 35-45 is a good place under stress but it generally depends on the CPU.

Intel's Pentium 4 Prescott's can often hit 70 degrees (C), although they shouldn't run more tha about 75C

the Pentium 4 Northwood's shouldn't run more than about 60-65C

the Athlon 64's normally run at about 40C (or 50C if it's a dual core)
55C would be pretty high for an Athlon 64, or 60C if it's a dual core

Athlon XP's can operate between 60 and 70, although they really shouldn't. on stock cooling, they should be about 50-55.

post about ur cooling nightmares.