Windows 2008 Server Core Activation.

start /w slmgr.vbs –dli

it will show you the dialog box as below.

Now run the below command to check the Installation ID

slmgr.vbs -dti

Note down this installation ID, now call to the MS local activation center and write down the activation key which consists of eight blocks of six digits you receive in response to punching in the Installation ID.

http://www.microsoft.com/licensing/existing-customers/activation-centers.aspx

Now run: 

start /w slmgr.vbs –atp GUID ActivationID

Where ActivationID must be notated as one long 48-digit string.

Run the command to check your licensing information  to confirm that Server Core installation was activated properly.

start /w slmgr.vbs –dli

Do it Without calling to MS



First RUN the below command to check the Activation status.

start /w slmgr.vbs –dli

it will show you the dialog box as below

Now run the below command to enter the product key.

slmgr.vbs - <Your Key>

now run the below command to enter the proxy, if you are using the proxy server co connect the internet

netsh winhttp set proxy <Proxy>

now run the below command.

start /w slmgr.vbs -ato