The crack didn't apply correctly or antivirus deleted LaunchGTAIV.exe . Fix: Re-copy the crack from the _Crack folder inside the installation directory. Manually add the entire GTA IV folder to Windows Defender exclusions.
Do NOT install to C:\Program Files (Windows protection can cause save issues). Instead, use C:\Games\GTA IV or D:\Rockstar Games\GTAIV . grand theft auto iv gta 4 updated multi 5 repack mr dj tool