Avira AntiVir Rescue System is a Linux-based boot disc that will detect and remove malware from a damaged PC.

If a virus attack has affected your PC to the point where it will no longer start, then the Rescue System may help restore normal operations. And if you think your PC is infected by something, but your regular antivirus tool can't find it, then this could be a useful way to get a second opinion. Booting from a separate CD means that stealthy malware like rootkits will find it more difficult to hide, and you'll have a much better chance of detecting and removing them.