I've been running SQL Server Express 2005 and the Express Management Studio for all my DB development. Ever since SQL Server 2008 came out I've been thinking about upgrading and today I decided to. However, after I upgraded I noticed that my SQL Management Studio didn't upgrade. After a few minutes I couldn't figure it out so I did a web search and found that Luis Rocha had already figured out the solution to the problem.

You can read his solution here. Some of the screen shots weren't working when I read it and I think he mis-named one of the items to click on Step #4 but much thanks to him for figuring it out.

Essentially, the solution is to close the installation program after upgrading SQL Server. Then, re-run the installation program and select Installation->New SQL Server stand-alone installation or add features to an existing installation. When you are prompted for a new install or add features then select your current instance. Finally, on the feature tree you can select the features to add including the Management Studio.