Knoppix and other linux live CDS are great, but you can also use a windows live CD with BartPE - http://www.nu2.nu/pebuilder/

You can find plenty of plugins for BartPE, including antivirus and spyware programs you can run directly from the windows live cd. If that fails, you can always recover your files with the liveCD and start from scratch.

Plugins:
http://www.smithii.com/files/plugins/
http://www.paraglidernc.com/plugins/plugins.htm

There should be adaware and an av on those...