This is caused by a driver performing an illegal operation in kernel mode. Try to think when this problem started and what drivers were installed approximately at that time and you may identify the problem.

I just came across this:

http://www.microsoft.com/technet/treeview/default.asp?url=/technet/prodtechnol/winxppro/reskit/prmd_stp_fwal.asp


Dell 4300 XP Home Edition
Pent 4 1.6HGz
40 GB Western Ditigal
128 MB Sdram (Duh)
ATI Rage Ultra 16MB
NEC NR 7800A Cd RW/Floppy
Conexant HSF V92 Modem
Creative SB Live Sound
Altec Lansing Speakers & Subwoofer
Epson 880 Printer
HP ScanJet 3400
ZoneAlarm
Norton Antivirus 2002