When you install Visual Studio 2005 or Visual Studio 2008, you can optionally install SQL Server 2005 Express. Starting with ASP.NET 2.0, Microsoft needed a database to contain data for its membership providers, and SQL Server Express is now its preferred database for those types of requirements.

One problem I've had with the default installation is that I also wanted to have SQL Server 2005 Developer Edition installed. The Developer Edition includes all the features that are in SQL Server 2005 Enterprise Edition, including SQL Server Analysis Services, Reporting Services, Integration Services, and the Management Console and other tools.

The difference between the Developer and Enterprise editions is in their licensing. Try as I might, when I put the install DVD into my machine and tried to install the Developer Edition, I was continually stopped by the existing SQL Server Express edition.

Our development team recently acquired some new PCs, and the solution we hit upon was to install SQL Server Developer Edition before installing Visual Studio. This works great for new installs, but it doesn't help if you already have Visual Studio installed. Even uninstalling Visual Studio and the SQL Server Express Edition didn't seem to help. There are remnants of the Express Edition still on the PC, blocking the upgrade.

In the past few days, I started working on a PC with Windows Vista that already had Visual Studio 2008 installed. Hoping that something would be different, I decided to try installing SQL Server Developer Edition again. As usual, I was blocked, but this time I noticed a helpful hint. I don't know if I just didn't see the hint before or if it is appearing as a result of something on the Vista machine.

The hint is this: don't start the install process for SQL Server Developer Edition directly from the GUI. Instead, open a Command Prompt window and navigate to the directory on the DVD where the setup.exe program is located. At the command prompt, start setup.exe with the command parameter:

SKUUPGRADE=1

Upon entering the parameter, I had access to all the install prompts, features, and options. Within a short time, I installed the Developer Edition along with the already installed Express Edition.