When you say "erased" One Care I assume you mean uninstalled it. If so, run the install cleanup tool -
http://forums.microsoft.com/WindowsOneCare/ShowPost.aspx?PostID=828910&SiteID=2 then go to -
http://onecare.live.com/standard/en-us/install/install.htm to install One Care. After installing open One Care and select "Subscribe" and when asked to enter a Live ID use the Live ID and password used to purchase your One Care subscription. Your subscription will be recognized and One Care will activate.
Windows live OneCare Installation
and then signed up for it after when I had two days left on the temp. program. Now after downloading and paying for the One year program I don't know how to download it as I did not receive a download link or a code key to start the program up?
