overheating problem

i recently been having heating problems that cause my system to crash completely, meaning it wont even post unless i remove the processor and reinstall it. even at stock speeds it will overheat just doing simple tasks.
here are the specs:
p4 2.53 533 mgz processor
asus p4pe mb
1 gig corsair 3200 memory
i have two 120 mm case fans and the stock heatsink and fan on the cpu.
i tryed to turn down the core volts and its on the lowest setting 1.5v and i even underclocked it to 2.44 but the same thing happens.
system ran fine now for 2 years and all of a sudden now it heats up and crashes. any ideas why ?
44c at idle high 50's c under minimal load

i also posted this in the cpu section but it is a asus mb.

Questions

If those temps you listed are your current temps, then temperature is not causing it to crash. Unless of course you know what the temp is when it shuts down?

What happens when it crashes? Does it reboot? Does it just shut off? Have you looked in the windows event log?

try clearing the cmos, it has a habit of fixing random problems

what is the voltage output of your psu rails? try another psu?

i cleared the cmos by using the jumpers and removeing the battery.
the psu volt is a little inder 12v right around 11.4 but my main pc is the same way, 12v is a little low.

when it crashes it will not even post, i get the voice mesage saying system failed cpu test. i think this board has a temp limit of 60c for the cpu and causes it to shut down if it reached that.

Is the cpu cooler clean and free of dust? is it working properly?

on older boards, a bad battery used to cause all kind of problems.

yea the cooler is clean and fan is turning. the fan rpm is around 2200 rpm- that seems kinda low to me cause on my other pc its at over 4000 rpm.
i did change the cmos battery and it didnt help.

well it died completely now. i can not get the pc to post at all not matter what i do. i tried removeing everything from the case but the mb cpu ram and video card and nothing. i reset the cmos with the battery and the jumper, reseated the cpu and hsf and nothing.
just wondering, does overclocking reduce the life span of a cpu even if you have low temps? and if so about how much does it reduce it ?