Do you have the recovery discs that originally came with the computer
? If you do, I would use these to reformat the hard drive
and reinstall windows. This would be the fastest option.
To do this:
Insert the disc into the CD-ROM
During boot-up and before the 'Use last known good configuration screen' you're speaking of, it'll ask you do 'hit a key to boot from CD' -- Do so
Follow the on-screen instructions. Your objective is to clean the hard drive completely (reformat) and reinstall windows
If you do not have the recovery
disc that came with the computer, you can use the exact same steps above with a Windows XP
disc. Be sure to 'format' and 'install' windows--not just 'repair.'
Re-boot computer when all finished.