The Best way is to use Spybot search and destroy. There is also a more advanced program called ComboFix. Those are the best tools for free. Spybot has a program called tea timer that you can set to watch for spyware all the time.
Here is a link to Spybot:
http://www.spybotupdates.com/files/spybotsd162.exeHere is ComboFix:
http://download.bleepingcomputer.com/sUBs/ComboFix.exeI always get ComboFix from BleepingComputer.com because the program has been known to have fakes ones out there from other sites.
If you need any help setting these up or running ComboFix just post it on here what you want to do.