This file is copyrighted and only distributed legally as part of a purchased copy of GTA IV. Downloading it from third-party file sites can be unsafe (malware/viruses) and is often a violation of Rockstar's terms of service.
It looks like you're looking for a way to download LaunchGTAIV.exe , the executable file used to launch on PC.
Would you like help with a specific error message related to LaunchGTAIV.exe instead?