This is a V-Ray application that is common across all V-Ray installations.
The VRImg to OpenEXR converter is both a command-line utility and a simple GUI application that can be used to convert .vrimg image files to .exr files in OpenEXR format. The .vrimg file format is a special format used by the to store the rendered image incrementally while rendering, in full floating-point format, with all available render elements. The V-Ray Image to EXR Converter converts .vrimg files to EXR format so the render elements may be loaded into compositing software, where they can be used for Back-to-Beauty compositing or for other adjustments and fine-tuning at the render element level.
This tool comes with the V-Ray for Maya installation. You can start it from the shortcut in Windows Start > All Programs > Chaos Group > V-Ray for Maya 20xx for x64 > Tools > VRImg to OpenEXR converter or manually running it from its executable in the V-Ray bin folder in the Chaos Group folder where your applications are installed:
Windows: start the vrimg2exr executable from C:\Program Files\Chaos Group\V-Ray\Maya nnnn for x64\bin\
Linux: start the vrimg2exr executable from /usr/ChaosGroup/V-Ray/Mayannnn-x64/bin/
Mac OS X: start the vrimg2exr executable from /Applications/ChaosGroup/V-Ray/Mayannnn/bin/
Note: nnnn is the Maya version.