Avira AntiVir Rescue System is a Linux-based application that allows accessing computers that cannot be booted anymore. Thus it is possible to:

• repair a damaged system,
• rescue data,
• scan the system for virus infections.

Just double-click on the rescue system package to burn it to a CD/DVD. You can then use this CD/DVD to boot your computer.

The Avira AntiVir Rescue System is updated several times a day so that the most recent security updates are always available. The version is updated several times a day, as .iso image or .exe file, and it includes its own burning software

http://www.free-av.com/en/products/index.html

Other Free Tools from Avira:
Avira AntiVir Removal Tool
Avira AntiRootkit Tool
Avira Boot Sector Repair Tool
Avira UnErase Personal
Avira NTFS4DOS Personal

Note:
The new version 3.5 of the Rescue System includes an optimized user interface, that allows the user to check the computer with only a few mouse clicks. The detected threats can be renamed, repaired or simply logged with the rescue CD. Avira’s free Rescue System runs on both Windows 98 and Windows XP or Vista systems.