Maybe I found a solution.
It was raised in a Win7-Forum and is also a solution for Vista.
There it is:
But my problem is, that I cant find any...
I try to play GTA IV on Windows 7, but the RGSCLauncher.exe wont start.
Googled for some days and maybe I found my problem.
I have to activate "Windows Communication Foundation non-HTTP Activation" on the menu for activating Win-Features, but it always fails.
I get an error...