Installation of Windows Live OneCare in Windows 7 is not supported. You can use the free Microsoft Security essentials for malware protection - http://www.microsoft.com/security_essentials/resources.aspx
See this post for End of Life information for Windows Live OneCare - http://social.microsoft.com/Forums/en-US/onecaregeneral/thread/81996436-edad-41ba-bdfc-02fc094e2ca9And, here's the FAQ on how to delete backups: http://social.microsoft.com/Forums/en-US/onecarebackupandrestore/thread/f0281206-ed0b-474c-8541-cc50843e5be2The instructions for Vista will work fine on a Windows 7 machine.-steve