I was having untold problems installing a new VM.  Windows 2008 with MOSS 2007, Visual Studio 2008 and SQL Server 2005.  Because I was building in that order I kept having problems after installing SQL Server.  Basically it didn't install the Management Studio or add the shortcut to the start menu.

 I tried for a long time to figure the problem out before I stumbled on a solution.  If you change the directory name C:\Program Files\Microsoft SQL Server\90\Tools before you do the SQL install (it's there because VS 2008 intsalls SQL Express) then the SQL install works fine and installs the Management Studio.

 I can only think that the SQL install finds the tools directory and then just assumes it doesn't need to do that bit of the install.  More likely it tries to create the directory, get a DIRECTORYEXISTS exception and tries to resume.

 Copy the old tools files back the the new tools directory when you're finished otherwise you might find VS has some problems!

Anyway, hope this help someone - I found nothing on google - maybe I'm the only one ;-)