Parasite removal programs.

Nothing is revealed in your post that would be a clue. As such, I'll offer a generic advice that all pests be removed and that you try the machine with the cover off to see if the issue is heat. You also will check to see if update Video, Audio and Printer drivers are available and installed.

http://reviews.cnet.com/5208-6132-0.html?forumID=32&threadID=1313&start=0 notes the five scanning tools and removal tools that are fairly safe. If one does encounter an issue, its always been damage done by the MALWARE. The most common issue being Layered Service Provider replacement which you can use LSPFIX (Hint: use http://www.google.com to find).

The thread has follow on discussions about new links if you don't want to use Google to find an item.

Bob

PS. All the tools are free.