|"i m facing this problem many time"|
Then it would appear that you're either installing some crappy software or corrupt driver after Windows has been reinstalled, or you have a hardware problem. I don't know why you're still running SP2 when SP3 has been available for over 4 yrs?
Boot off the XP disc, press R to start the recovery console, then type chkdsk /r & see if that helps. If not, boot off the disc again, press R again, then try running FIXBOOT & FIXMBR.