I installed this a few months ago and have to say nice job Microsoft. It is a free download if you have an authentic copy of windows XP.

http://www.microsoft.com/athome/security/spyware/software/default.mspx

I also use an online spyware scanner at
http://www.spywareinfo.com/xscan.php

I agree. I've had it since it was out on beta. so far, no problems.