Jim, try checking the key with a magnifying glass. I find that the characters are miserable to discern at times.
Are you getting an error that the key is invalid or that it has been used already?
You can contact support via email per the instructions in the FAQ for a trial user. (You may have gotten a forum alert when Danzig posted the support number, which I had to delete as it is not allowed to be posted since trial users may only use email support and paid users must validate their subscription in order to see other support options.)
How to reach support (FAQ) - http://forums.microsoft.com/WindowsOneCare/ShowPost.aspx?PostID=2421771&SiteID=2
-steve