While installing SQL Server 2008 on a 64bit machine with Visual Studio 2008 SP1 installed you may come across a dependency check error:
Rule "Previous releases of Microsoft Visual Studio 2008" failed.
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.
This error is documented on KB 956139, "Actions that are required before you install SQL Server 2008 on a computer that has Visual Studio 2008 or the prerelease version of SQL Server 2008 installed".
I had Visual Studio SP1 (version 9.0.30729.1 SP) properly installed on my machine, so why this message? Well, with a quick monitoring using Process Monitor I noticed that the setup process was looking for ServicePack information on the WoW64 registry key, that was outdated:
In order to fix it, you can update the SP and SPIndex entries to 1 and the SPName to SP1; just like the registry key at HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\DevDiv\VS\Servicing\9.0\BSLN\1033:"