It means that your GTA IV is cracked (Not 100percent sure )
No, you can't crack GTA IV with a commandline.txt.
If your "FATAL ERROR" problem still persists, it means your game isn't cracked (if it's pirated) or you have to update your game.
I strongly recommend you to update your game from
this link and try to run it again by clicking "LaunchGTAIV.exe."
If it's pirated, then go and find a proper crack for your game includes "xlive.dll" (this is important).
It's also advised that you update both your video drivers and Games for Windows Live Client after installing the game update:
Games for Windows LIVE