Knoppix can not safely write to or delete files from an NTFS partition. Your best bet might be to boot Knoppix, use Knoppix to recover any files that you need to save (to floppies, usb flash drives, external drives (with FAT partitions), CD/DVD drives, install an extra drive with FAT partitions, storage space on the Internet, or across a network to another computer) and then reinstall a clean version of windows. And if you don't have a hardware firewall (DSL/Cable router), you might not want to even bother. There are plenty of horror stories that people can't get XP on the Internet long enough to load the "security updates" before they are infected with something (not that these updates are very effective, either), including this story of a typical Windows system going down after 4 minutes of DSL access.