You can try SpyBot. Visit www.safer-networking.org where you can download a free program with free updates. Very good program, will help you remove spyware/malware/adware. However worms and viruses will require removal tools. Visit symantec.co.uk for removal tools but you will have to know what virus/worm it is.
Failing all, I would suggest a format and recovery using your copy of windows
Kash, April 2006