The first public beta of Windows OneCare Live is now available. This is essentially Microsoft's new anti-virus solution, which is apparently based on the software by the Romanian anti-virus company they acquired some time ago.
It seems to be tying in to Windows Live somehow, though I haven't had a chance to test it out yet. I'll post back here when I do. For now, you can get the beta from here, although you need to open this link in IE6 to actually get the file, as well as supply your email address.