Hey MrDanke,
When you installed GTA 4 and IVMP, have you installed the patch 1.0.7? It is required to get the IVMP working.
You can check
this topic for more information about how to install the game.
Edit: The one that opened for you seems to be the normal game menu and not the IVMP. So make sure to install the version of client we currently using, and the 1.0.7 patch (check the topic above).