Spy Sweeper is my new anti-spyware solution of choice. I started out using Ad-Aware, but I ran across spyware that I was trying to remove that Ad-Aware could not take care of.
At that time, I stumbled upon both the Microsoft Anti-Spyware Tool and Sunbelt CounterSpy. Both tools did an exceptional job, and went with CounterSpy because it was advertised as the creator of the engine for both products.
In two years of use, CounterSpy bogged down my 2.8Ghz P4 with Win2k and 1 GB RAM. I also had quite a few false positives in those two years. With a recent update, CounterSpy constantly disabled itself on my Win2k system.
I decided to switch over to one of the top recommendations from a Consumer Reports article… Webroot Spy Sweeper… as far as I can tell so far, Spy Sweeper is using only 8MB of RAM while not conducting a scan.