Windows Server 2008: display and extend Windows activation grace period

Problem:

If you install a Windows Server 2008 without product activation, your machine will be set in a 60 day grace period. What is to do if you want to check how many days are left in current grace period, and how can you extend the grace period?

Solution:

To determine the grace period left days, open a command prompt and run  
slmgr.vbs -dli

To extend the grace period for next 60 days,  open a command prompt and run 
slmgr.vbs -rearm

You can extend the grace period 3 times by 60 days again, for maximum 240 days.



Both commands will deliver a popup window after a few seconds stating the desired information.

You find more detailed information in KB948472.