***UPDATE Nov 2, 2016*** Starting in TFS 2015 Update 3 and beyond, this trial extension process has been removed. We have moved to and “honor based system”. A trial will expire and the product will inform you of that but it is up to you to stop using it at that point.
The old process for TFS 2005 and TFS 2008 is no more. It’s now baked into TFS 2010 and later. The TFS 2010 and later trial period is 90 days. However, after the first 30 days, you will start getting this dialog every time you run the admin console to remind you how much time you have left on your trial and allowing you to enter the product key from a purchased product to turn the trial into a fully licensed product (no need to uninstall, install, repair or anything of the sort).
You can hit Cancel and keep using your trial until it expires.
You can also, at any time check on the state of your trial by clicking on the top node in the Admin console navigation tree and see something like this:
As you can see, it tells you when the trial will expire and has two actions: Update License, which will display the dialog I showed you above, enabling you to enter the license key from your purchased product; and Extend Trial Period, which allows you to continue with your trial a little longer. The first 30-day extension is “hassle free”. Just click the Extend Trial Period button and your trial will be extended 30 days. After that you will need a new Trial ID for additional 30 day extensions.
To get this, you will need to get a new Trial ID. You will need to supply your existing Trial ID when contacting us; this existing Trial ID is displayed when you click the Extend Trial Period link. The Extend Trial Period link won’t be visible unless you are within 60 days of your trial expiration. Once you have your existing Trial ID, email firstname.lastname@example.org and we will help you.
You can also do all of this on the command line using the tfsconfig.exe program. Here’s the result of running tfsconfig license /? and tfs config license:
Let me know if you have any questions.