When you can't run programs because of viruses

Brian has mentioned RKill which comes in a variety of files to run, but has anyone used this tool from Symantec?

UnHookExec.inf

Using Symantec�s tool to reset shell\open\command registry keys

Sometimes worms and trojans will make changes to the shell\open\command registry entries as part of their infections. This will cause the virus to run each time you try to run an .exe file such as the Registry Editor. Right-click on it and choose Install. Restart your computer and then you should be able to run the program.

http://www.symantec.com/security_response/writeup.jsp?docid=2004-050614-0532-99

So if anyone has any other tools please share.

Regards,
Another PC Technician