I was helping a colleague setup their new Windows 7 developer box today, and we couldn’t install SQL Server 2008. SQL Server’s installation would complain:

A previous release of Microsoft Visual Studio 2008 is installed on this computer. Upgrade Microsoft Visual Studio 2008 to the SP1 before installing SQL Server 2008.

Well, we’d already installed Visual Studio 2008 and Visual Studio 2008 SP1 so why wasn’t it working? Even after a reboot Visual Studio 2008 was reporting that SP1 was already installed.

In the end we had to install VS 2008 SP1 a second time, and after that the SQL Server install worked fine.

What went wrong? The developer had started to install SQL Server 2008 while VS 2008 SP1 was still being installed.