If I'm not mistaken, I believe Microsoft made the decision to get out of the Anti-Virus etc., business and are not going to be offering Live One Care anymore.
Also, consider purchasing a router (which should include a firewall) for installing between your PC and "The Bad Guys" [your PC and the Web] (probably your best protection).
I've never had an "issue/problem/virus" since incorporating the above.
Your risks go up if you have other users on your PC and/or do a lot of copying/downloading from flash/floppy/PeertoPeer/thumb drives/websites.