I have been do many research of them there would many of users complain why i always get the RSGC error:application failed to launch.
Problem is :
did you change your file install when you install GTA 4?
If you change the file install.Good this would why you here to visit my topic .
For those who dint change the file install sorry you should call GTA IV support .
Solution Work for Every Window.
Step 1:go to start>run>regedit
Step2:expand(double click the file) HKEY_LOCAL_MACHINE
Step4:Expand Rockstar Games
Step5:Select Grand Theft Auto IV
Step6:Double Click Install Folder.After that go to your GTA 4 directory
Step7:Paste the word where you install in the tab:value data
Example:F:\Grand Theft Auto IV
Original would be:C:\Program Files\Rockstar Games\Grand Theft Auto IV
HOPE THIS HELP YOU