I'm assumed that you've perform a clean installation of Windows Server 2008 64x Edition.
Use Server Manager snap in, right click on the Roles container and then choose Add Roles. The system will now launch Add Roles wizard.
Click Next to bypass the wizard’s Welcome screen. Select Hyper V check box and then click Next.
You will see the Introduction to Hyper V which describe about Hyper V. click Next.
You will be ask to select NIC to create virtual network. Select the LAN 2 NIC card and Click Next
Then you will see a screen confirming the installation of Hyper V. Just click Install. When the installation complete, the system will prompt for server reboot. Just click Yes to reboot the server. When the server reboots, log back into the server and the Server Manager should automatically load and resume the installation process. After about a minute, you should see a message telling you that Hyper-V has installed successfully. Click Close to complete the wizard.
Note: For RTM version, you must download and install KB950050.
http://www.microsoft.com/downloads/details.aspx?FamilyId=6F69D661-5B91-4E5E-A6C0-210E629E1C42&displaylang=en
