You may wanna check requirements especially if you have Visual Studio 2008 installed.
SQL Server 2008 RTM requires Visual Studio 2008 SP1 (not available yet) so you may have a problem. I did.


Solutions:
  • Uninstall Visual Studio 2008 pre SP1 components (SP1 beta won't work either)
  • Wait for the SP1 (should be released soon)
  • When you install SQL Server 2008 make sure you don't select features that use the VS Shell (BIDS, Analysis Services, Integration Services).

Thanks to Bob Ward we have the problem documented here: Microsoft SQL Server 2008 Release Notes