Go to www.microsoft.com and go to the newsgroup.
There you will find that MSAS is still in the Beta stages. YOU will find testimonials from people who say MSAS has crashed their computer completely and statements from microsoft employees that say MSAS gives alot of false positives. The link given two posts above (thanks LOTR) will tell you that Spybot and AD-Aware are the best anti-spyware out there. Limewire is safe. (Unless of course you don't check your files before downloading them as many of us have learned the hard way. But this is not Limewire these are unscrupulous users.)

Don't believe everything Bill Gates tells you.