Here are a few links to sites and programs that are useful if you think you may have a virus or spyware installed on your computer. Most will have functional free versions, just be sure to follow the links for the Free/Basic versions, the Full/Premium versions are often free trials.

Security Page Windows Updates info, Fixit's etc.

AVG Free Fully Functional Anti-Virus.

Microsoft Security Scanner Standalone scanner.

Spyware:

Malwarebytes Free Trial Anti-Malware Scanner.

Spy Bot Free Anti-Malware Scanner.

Utilities:

Ninite The easiest way to get apps -- customizable installer.

Download Various tools.

CHMOD Tool