Hi lilacnsmay, welcome to SAF
Not so much we can do if you can't access the keyboard. It must work on BIOS access, as nothing is loaded during this process. Have you tried to boot in safe mode ? (safe mode prevents most processes to run, including virus)... if you can't, the only way is to boot from a protected floppy, reformat and reinstall Windows.
For now, try to access BIOS settings, set boot order to the CD-ROM first and disable any other boot options. Try to boot from your Windows CD and perform a repair install as explained here:
http://support.microsoft.com/?kbid=315341Chris