How to install Windows Server 2008 without activating it

1. Run the Windows Server 2008 Setup program.
2. When you are prompted to enter a product key for activation, do not enter a key. Click No when Setup asks you to confirm your selection.
3. You may be prompted to select the edition of Windows Server 2008 that you want to evaluate. Select the edition that you want to install.
   
   Note After Windows Server 2008 is installed, the edition cannot be changed without reinstalling it.
4. When you are prompted, read the evaluation terms in the Microsoft Software License Terms, and then accept the terms.
5. When the Windows Server 2008 Setup program is finished, your initial 60-day evaluation period starts. To check the time that is left on your current evaluation period, run the Slmgr.vbs script that is in the System32 folder. Use the -dli switch to run this script. The slmgr.vbs -dli command displays the number of days that are left in the current 60-day evaluation period.

How to manually extend the evaluation period

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:

1. Click Start, and then click Command Prompt.
2. Type slmgr.vbs -dli, and then press ENTER to check the current status of your evaluation period.
3. To reset the evaluation period, type slmgr.vbs –rearm, and then press ENTER.
4. Restart the computer.

This resets the evaluation period to 60 days.

 

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