Hardware Problem

I’m having a problem in my system whenever i boot my system after the login page when i reach my desktop it hangs and then i hav 2 restart it again and again it hangs. sometimes it hangs and sometimes it automatically switches off and some time it dosesnt boot, i dont know wat is going on…plz help

my configuration is :
Intel Motherboard D845GVSR
Intel P4 2.40 GHz 533 system bus 1Mb L2 Cache Processor
XP SP3 all drivers up to date
Kingston 512 Mb DDR1 RAM

Try booting into Safe Mode and run a virus/malware scan. It could be anything from a failing power supply to memory problems.

I have run a scan n found nothing i think its a problem with the motherboard,