Install GitExtensions on a machine with .NET 4.0 only

Question

.NET 4.0 / Visual Studio 2010 is installed on my machine. When I execute the current installer (GitExtensions224SetupComplete.msi) it tells me that I need to install .NET 3.5.
Can one use GitExtensions with .NET 4.0 or do you have to install .NET 3.5? If yes, how do I force the installer to use .NET 4.0?
Is there a general approach to this, which also works with other programs and installers?

Thanks