A: Installing VMware vCenter Server 5.0 requires you to first install Microsoft .NET Framework 3.5 SP1. You can launch this prerequisite installation from the Windows Server 2008 R2 server's Server Manager; however, there's a trick to doing it correctly.
Start by right-clicking the Features node in Server Manager, then choose Add Features. In the wizard that appears, click the plus sign next to .NET Framework 3.5.1 Features, and select the check box titled .NET Framework 3.5.1. Do not select the check box titled WCF Activation because this option will install components of Microsoft IIS that will later conflict with vCenter Server 5.0.