If you have installed Windows Live OneCare and have run a full scan, that would mean that it hasn't found any. If, however, your PC is exhibiting behavior that you think is caused by malware that has gone undetected, please contact support.
If you are using Windows Live OneCare and you have been infected, but OneCare did not detect or cannot remove the malware, please contact support to report this and for help with removal.
How to reach support (FAQ) - http://forums.microsoft.com/WindowsOneCare/ShowPost.aspx?PostID=2421771&SiteID=2
If you are in North America, you can call 866-727-2338 for help with virus and spyware infections. See http://www.microsoft.com/protect/support/default.mspx for details. For international information, see your local subsidiary Support site.
-steve
