To re-arm and extend the grace period use:
- Click Start, and then click Command Prompt.
- Type slmgr.vbs -dli, and then press ENTER to check the current status of your evaluation period.
- To reset the evaluation period, type slmgr.vbs –rearm, and then press ENTER.
- Restart the computer.
The server will cease to function correctly once it reaches the end of the grace period and it has not been activated or the grace period has not been re-armed.
To view the licensing information, use slmgr.vbs –dli
For more information about this topic, see: http://support.microsoft.com/kb/948472/en-us