If you have booted knoppix, click the Harddisk icon (hda1) on your desktop. A konqueror browser window will open in wich you can view your windows system-files.
If you're looking for a program to scan viruses, you might consider using Linux Bit Defender wich is based on knoppix and has a build in virusscanner. Look on this website.
http://www.distrowatch.com/?newsid=01481#0