A client called with slow laptop performance, constant Windows error reports and no wireless internet.
At first I suspected a virus, but the pc was showing none of the classic virus/spyware infection traits (pop-ups, changed background, brower hi-jacking).
After looking through the event logs I determined that the slowness and windows errors were being caused by a 3rd party power management tool. The client never remembered installing it and it was not part of the original factory shipped software.
Uninstalled it, fixed the issues. The wireless internet was another problem, but easily fixed.