For the last 2-3 months, all too often my system will lock/freeze up . . . random program(s) running, online or offline, or just idle . . . hard drive write light goes into a steady slow on-off CYCLE . . . Ctrl-Alt-Del doesn't work, reset button on PC doesn't work, power off button on PC doesn't work . . . only recourse is to pull the PC power plug.  Reconnect in couple minutes, punch PC power button on & system starts. May or may not get warning window that Windows is checking the file system on one of my drives; if so, files (so far) get Window's ok & I'm back in business until the next time - - which may be minutes or hours or days.  Running Win-XP (all current updates) on Pentium IV ; 256Mb RAM; lots of FREE disk space on all drives; defrag, virus & spyware scans are run religeously; have not added any new hardware recently.
     Any hints as to what is going on will be greatly appreciated . . . I'm getting very nervous, and these constant system backups are a pain !!!
     Walker DixHave a LOOK at this post and follow the instructions. Pay particular heed to the LINK regarding virus/trojan/malware removal.