You can get your PC scanned online for security vulnerabilities. Its a good way to test for spyware, virii, or open ports. Here are a list of sites you can check out for this:

http://hackerwhacker.com/

http://scan.sygatetech.com/

http://www.testmyfirewall.com/

http://www.auditmypc.com/

http://www.iggyz.com/Test.html