Such a crazy error this one.
Thank the Internets that we have Aaron Stebner to help us. Aaron just happens to be a senior Microsoft developer who worked on multiple versions of the .NET Framework amongst many other things, so I think he can be trusted or, as we like to say here at BTWT, bitten.
So the issue you are probably facing where you get that weird ‘compatibility mode’ error dialog is, to quote Aaron:
you exited setup after it told you that VS 2008 was open, a dialog appeared that said that the setup didn’t appear to complete successfully. If you clicked Yes on that dialog, it will cause future attempts to run that installer to launch in compatibility mode, which will then trigger the error in this blog post. Compatibility mode is stored in the registry based on the full path to the setup program, so it will appear every time you launch setup from the same location as it was originally launched from. Renaming or moving the file will cause the path to be different so it won’t trigger the compatibility mode dialog.
So just move your setup.exe or vm_web2.exe to a different directory and double click.
It will run.
It will install.
You will keep your job.
A couple of other fixes for the problem are described on Aaron’s page.