Windows Server 2008 R2 Evaluation (180 days)

How to manually rearm the 10 day activation grace period
When the initial 10-day activation period nears its end, you can run the Slmgr.vbs script to reset it back to 10 days. To do this, follow these steps:

1. Click Start, and then click Command Prompt.

2. Type slmgr.vbs -dli, and then press ENTER to check the current status of your activation period.

3. To reset the activation period, type slmgr.vbs –rearm, and then press ENTER.

4. Restart the computer.

This resets the activation period to 10 days, and can be used up to five times. After this you will need to either activate or reinstall the evaluation.