I have P-IV processor, 865GBF motherboard with HT enabled. The problem
is that, at times while running applications it "restarts". If i monitor the
processor's temperature from the setup it always show temperature in high
40s and 50s. It has also been rebooted once when the temperature was
approx. 38deg centigrades. This shows that the problem is purely statistical.
Can anyone solve my problem???

One thing more, at times i continously run my pc for about 24hours without
any kind of restarting problem.

I would suggest running the Harddrive diagnostics which can be downloaded from the manufacturer's web site.

Also, I would run a RAM checker:

http://www.memtest86.com/

Thanks a lot.