I will never understand why some software/hardware vendors fail (forget?) to clean up the Windows registry after they've... well, fondled with it for reasons known only to them, such as during software installation or updates.
When installing SQL Server – the release or a service pack – on a machine where software from one of the aforementioned vendors has recently been installed or updated, the installation may fail with the following error message:
Rule "Restart computer" failed. A computer restart is required. You must restart this computer before installing SQL Server.
Although the solution to this problem may sound very straightforward, restarting may not always be enough (or even possible). Actually, in some cases a restart may not be needed at all – i.e. if the machine has already been restarted following the offending installation/update, but the registry hasn't been cleaned up automatically.
This is a very well known issue and a workaround has been known ever since SQL Server 2000 (e.g. KB 312995), and is not really a big deal anyway – only a single value needs to be removed from the registry.
So, if this is such a well known issue then why am I writing about it? Honestly, whenever I encounter this error I never seem to remember the exact name of the registry key that needs to be changed. Which can be somewhat frustrating. Not anymore!
What to do (in 69 words or less)
Warning! Changes to the registry may cause serious problems and even require re-installing the operating system!
Before attempting any changes to the registry, make sure you create a backup of the key you intend to edit (using the Export command in the Registry Editor).
The following registry key needs to be changed in the case of unsanitary installs:
The value that needs to be removed is