-or press F8 at boot --> Safe mode. That'll give more freedom with deleting any files required by system at boot, for reasons legal or otherwise. One of the best tools I know for detecting "gray area" malware is found at
www.webroot.com (trial only, will not delete bugs). Still, browser malware and "true" viruses are mutually supportive, the patches must be applied at all times!
http://www.computerhope.com/issues/chsafe.htm