I suggest Spybot or Spykiller.
Will they get rid of spyware that is already infecting the computer?
Both are good... for being "free"
If you want it to NOT start randmly eating certain components of your comp (sometimes if you don't know what you're doing, you can get rid of windows applications.)
I recently went to Best Buy and purchased($30) Webroot SpySweeper.
No problems since.
It also gives you more info on what you're getting rid of before you get rid of it (so you can choose to NOT if you like)
Simple interface, and now my roomies can't even find my files using the network watchers they got. (The watcher operated off the fact that I HAD spyware on my comp.)