Extend Vista or Windows Server 2008 Activation-free Evaluation Period

http://www.mydigitallife.info/2008/06/08/how-to-install-and-use-windows-server-2008-240-days-for-free/

http://support.microsoft.com/kb/948472

How to manually extend the activation grade period on expiring

When the 60-day activation grace period is about to expire and end, run the slmgr.vbs script to reset and extend the evaluation period for another new 60-day trial evaluation period, with everything including programs installed and data intact.

1. Open an elevated privilege command prompt.
2. Type the slmgr.vbs -rearm, and then press Enter to reset the activation grace period to 60 days.
3. Restart the computer.

To check the status or time that is left on current activation grace period or evaluation period, run slmgr.vbs -dli command to display the number of days that are left in the current 60-day evaluation period.