PLEASE NOTE: You need to have Windows Live account created before running the game, otherwise you won't be able to save the progress.
1. Install the game, including Rockstar Games Social Club.
2. Run the original LaunchGTAIV.exe while connected to the internet to bypass the release date check.
3. LaunchGTAIV.exe will now unpack into a smaller LaunchGTAIV.exe and paul.dll.
4. Now MAKE SURE you disallow internet access to GTAIV.exe, LaunchGTAIV.exe, and RGSC.exe (Rockstar Games Social Club application)
5. Replace LaunchGTAIV.exe and paul.dll with the ones from the crack.
6. Run LaunchGTAIV.exe.
7. Rockstar Games Social Club will start and prompt you to log, but just start it in offline mode/don't log it.
8. The game should now run.