Windows Server 2003 R2 comes on two product discs. Disc 1 contains Windows Server 2003 with Service Pack 1 (SP1) and Disc 2 contains the installation files for the Windows Server 2003 R2 files and optional components.
NOTE: Both discs use the same Product Key.
If you already have Windows Server 2003 with SP1 installed, you only need to use Disc 2.
Installing Disc 2 only installs MMC 3.0 (Microsoft Management Console) and prepares Windows Server 2003 R2 for the installation of optional components.
Once you install Windows Server 2003 R2, you CANNOT UNINSTALL it.
Once you install Windows Server 2003 R2, you CANNOT UNINSTALL SP1.
When the Disc 2 setup is finished, you can install the optional components by using the Control Panel / Add or Remove Programs / Add/Remove Windows Components applet.
NOTE: You can add or upgrade server roles using the Manage Your Server Wizard.
NOTE: If ADAM or SharePoint Services is already installed, you should upgrade them from Disc2.
If you ever do an in-place upgrade using Disc 1, you must reinstall Disc 2.
NOTE: DO NOT install Windows Server 2003 R2 on a 64-bit addition of Windows Server 20034.
Before you install, you should read the TechNet Windows Server 2003 R2 (Only) Deployment Guide.