Thank you lbyard.
i don't know how to set irq but No problem exist in my device manager.
another thing that i found is that enabling
turbo speed which means 103 MHz instead of 100 MHz
causes the computer to crush at the begining.
as an electrical engineer,when we design a chip,
we clock it 10%-20% faster to check the reliability. if it can't work at 103 MHz , sure it will crush sometimes on 100 MHz.
i tried to take out one component each time,
my sound card, display card, memory, etc.
non of this fixed the problem.
also i found that Norton utilities disk doctor, and speed disk causes the computer to freeze after 1 minute every time they work.
do you think that formating my hard drive and start from the begining can fix the problem ?
thank's again for your help