They have a tendancy to ignore possible futures and always test for exact current versions.
This is the case when you try and add the WPF and WCF addons to VS2005.
Here is an article on how to make it work once you have installed service pack 1 for .NET 3.0
The idiot who wrote the installer tested for the presense of the uninstall option for the initial version of .NET 3.0, ignoring the possibility of a service pack.
This is not the first time I have seen a microsoft installer perform this stupidity.
Back in the day I learnt a lot about the registry configuration for COM objects the hard way.
The 16 bit version of VB installed a common library. Subsequently this library had a 32 bit version released too.
If you installed the 16 bit version over the 32 bit one it clobbered the registry sufficiently to break the later version.
Rather inconsiderately the application suite that I was assisting used both versions…
I had to write a patch utility to correct this problem. COM always had a technique for handling this kind of versioning problem but it was clear that whoever wrote the installer did not understand this.