About 30 seconds of searching (yes I mean that literally) and I found the solution to the GTA IV problemhttp://steamcommunit...20616777193/#p2
All I did was type in Windows 8 GTA IV into Google...and it was 4 links down.
I will apologize in advance if you already followed those directions, but while typing this I did more research and a combination of the two things in that thread have led to a fixed situation for everyone that I've read about over numerous websites. I have yet to see it not work for anyone...but since you're already back on 7 it won't matter.
BTW as mentioned also...launching from Steam just won't work..something about the way it calls the launcher up causes it to screw up....there's a solution for that issue as well.