Upgrading TFS From Trial to Production

Here is a great article on how to upgrade your (most likely expiring) trial editions of TFS to the full production editions. You don't need to reinstall. Here is the link:

http://msdn2.Microsoft.com/en-us/library/ms404852.aspx

Also, here is a great blog post about it as well.

TFS Trial Edition and Release Candidate Expirations