I need to know this since this is a pre-req for .NET 3.5 and if I'm including the .NET bootstrapper, I should also see if Windows Installer 3.1 is needed.
Right now I'm checking for the registry key:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Updates\Windows XP\SP3\KB893803v2
Which will check for Windows Installer 3.1 but I suspect it doesn't check for higher versions. (Haven't been able to confirm or deny that)
What registry key should I look at to find this information?
Edit: I need to check this in Inno Setup which is what I'm using as my bootstrapper, and I'm not sure how to check a dll version in there.
Best Solution
locate the installer msi.dll with this registry path: HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Installer
value: InstallerLocation
then get the version information from that file.
update: the way above is old! new way to detect the version is documented here: http://msdn.microsoft.com/en-us/library/aa368280%28VS.85%29.aspx