When the initial 60-day evaluation period nears its end, you can run the Slmgr.vbs script to reset the evaluation period. To do this, follow these steps:
Click Start, and then type cmd .right click Run as administrator.
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.
This resets the evaluation period to 60 days.