There is only one file type that uses the .OIV extension:
OpenIV Mod Package File
Package used by OpenIV, a versatile editor and installer for games, such as Grand Theft Auto IV and Max Payne 3; contains an .XML file that holds a package description and scripts; may hold a .PNG icon for the mod; similar to a .ZIP archive.
OIV files are used to distribute mods that modify gameplay, such as models of vehicles. OpenIV can be used to edit, create, and install OIV files.
Updated: March 4, 2014