Alot of people is asking for How Can they know when their TFS installation is being expired ? simply use this tool,to know when your version will be expired and how to extend it as well :)
A dialog will appear and you need to press the "Check" button. If you are within 10 days of expiration of a trial of TFS, and "Extend Trial..." button will appear in the lower left hand corner. Press that and your expiration date should be extended to 30 days from "today" (today being the day you run you click the Extend Trial button).
download the tool :
COOL TOOL :)