Non-system disk error in WIN XP

My neighbors computer was just updated from Windows 98 to XP, before she could change the setting for the auto updates XP downloaded what I believe is the Sasser worm the at resets your computer when connected to the internet. The second time it reset her computer she called me as it was rebooting. When it tried to reboot it gave her a Non-System Disk Error message and nothing I have tried seems to be helping. I can get rid if the worm but I am stumped as to the error message and cant get back into XP to fix the worm problem. Any help would be greatly appreciated.

Thanks

Mark H

This may sound stupid, but... is there a disquette or CD in one of the drives?

Try to boot into safe mode, and get McAfee's Stinger to clean out Sasser.

It does rather sound like it is the floppy drive... or maybe a non bootable cd in the the cdrive. XP says "unmountable boot volume" if it's a hard drive problem.