Strange error message at boot-up...

Everytime I try to boot my laptop, after the Windows screen, a blank desktop appears with no icons or start menu, and the following message appears in a pop up box...

16 bit MS-DOS Subsytem
C:\Windows\System32\rmass.exe
The NTVDM CPU has encountered an illegal instruction
CS:0d9b IP:0110 OP:62 da da da

There are two buttons, Ignore and Close. Regardless of which button I click on, the box does not go away.

It does this even in safe mode. I can't get in to Windows at all. It is Win XP home service pack 1.


Thanks for any assistance.