Here you go, Jessica:
http://www.pctools.com/spyware-doctor/?ref=trial_mgsd
scroll down the page for a free scan

More to choose from:
http://www.majorgeeks.com/downloads31.html

One of the best freeware application is:
SUPERAntispyware - FREE
http://www.superantispyware.com/index.html
http://www.superantispyware.com/supe...freevspro.html

Suggest you have a close look at the URL provided by PA Bear:
http://wiki.castlecops.com/Roll_your...Security_Suite

Good luck :)