After gsx_p3d4_setup is downloaded, it prompts during installation: the source file is corrupted 
The source file is not corrupted. It might have been corrupted on your system, either for a download problem, or because your antivirus has mistakenly identified as a thread, and corrupted it trying to "heal" a non-existant threat.
- Disable your firewall
- Clear your browser cache
- Remove this folder
Documents\GSX_Installer
- Disable the antivirus
- Try the download again
