If you’re using the beta release of Windows AntiSpyware, be sure to get the latest update:
Since releasing Windows AntiSpyware (Beta) on January 6, 2005, we have received feedback from customers and have made enhancements to the software based on this feedback. We have enhanced some of the real-time protection agents, added new threat categories, and improved stability and performance. If you are using a previous version you can simply upgrade to the refreshed version.
I haven’t looked carefully at this yet, but based on the description it sounds like a fairly modest update.