As Devastator said, a system format is probably your best bet. It should go unsaid that you should be sure to back up your most important files (iTunes song files, photos, porn, work documents, ect.) on an external hard drive before doing this though.
Best of luck.
Best of luck.
The best way to be truly sure your laptop is clean is to nuke and pave (format and reinstall windows).
In the mean time, change your passwords for everything. Yes, everything. Do it on a known to be clean machine as well.