I've moved your post to the Install and Activate topic in the forum as it has nothing to do with the topic you posted to.
The symptom you are describing would happen if you have a conflicting security program on the PC. Multiple virus scanner engines active can cause this problem.
See this post for the KB article to troubleshoot install problems - http://forums.microsoft.com/WindowsOneCare/ShowPost.aspx?PostID=1588602&SiteID=2
If you are unable to identify the cause of the problem and resolve it, please contact support:
How to reach support (FAQ) - http://forums.microsoft.com/WindowsOneCare/ShowPost.aspx?PostID=2421771&SiteID=2
-steve