STOP error, Inaccessible Boot Device

Hi

I have a GX150 which will not boot.  Right after the Windows 2000 splash screen, I get a blue screen and stop error which Reads Stop 0x0000007b, Inaccessible_Boot_Device.

Before I received this error, I had discovered the Small_Comp.100 virus and deleted files which were quarantined.

I have tried to recover the last good boot, and used the Windows Emergency Disks and 2000 CD  to do a system repair using the recovery console, and updated the BIOS but with no luck.  Nothing was changed or added to this computer.  It does not have ROXIO software or a CD/RW.

My Antivirus support site offers little information regarding this virus and I do not know the extent of damage caused.  I know that Microsoft has Knowledge Base Articles regarding this error, but I was wondering if anyone can offer suggestions.  Is this a problem common to the Optiplex 150 as they get older or is this caused by the virus?

Are Dell Diagnostic/Repair software available which will help with this problem? 

Must Windows be reinstalled, but must a low level format be run first?

Thanks