The .NET Framework is meant to be backwards compatible, so if in my case I have v3.0 installed an application designed for v1.1 should work just fine. Well that’s the theory, however the installers for many apps won’t let you proceed, unless you have the exact version they were designed for installed. This is pretty damn annoying, since that application itself will in most cases run just fine.
The solution is to edit the .MSI installer package and remove the framework requirement check. To do this you need the Microsoft Orca MSI Editor, which is part of the 300MB+ Windows Installer SDK package. Fortunately some kind person has posted the 1.8MB Orca Installer separately.
Once you’ve installed that, open your offending application .msi in Orca and do a search for VSDCA_VsdLaunchConditions and remove every entry it finds. Save the changes and you’ll be ready to go, without the .NET Framework prerequisite check.