In Windows Server 2008 you can use the Server Manager application to enable RIS (part of Windows Deployment Services, WDS). To do so, open Server Manager and click on Roles in the left column. Then click on Next and read the Introduction to WDS items. It’s worth noting that you can setup your server as a Transport Server in WDS, which is a bit like Multicast clustering (eg – multicast ASR imaging for the Mac). It’s also worth noting that a Deployment Server will use parts of the Transport Server to do its job so you’ll need to install both. Once you’re satisfied with your selection, click Next and then click on the Install button to install the services.
Prior to installing WDS it would be a good idea to install DHCP, DNS and Active Directory, or at minimum verify their operations.