FileInfo.com - The File Extensions Resource

.VC4 File Extension

File Type 1	Virtual CD Disk Image (Most common)
File Format	File
Common?	No
File Description	Exact copy (image) of a CD-ROM, stored as a file on the hard disk; can be used to run CD-based programs without inserting the physical CD; common disc image format recognized by several disc authoring programs.
Program(s) that open vc4 files	Windows: H+H Software Virtual CD; Smart Projects IsoBuster; EZB Systems UltraISO; MagicISO

File Type 2	Visual C++ 4 File
File Format	Proprietary File
Common?	No
File Description	Makefile containing C/C++ source code created by Microsoft Visual C++; may be referenced by a Visual C++ project (.VCPROJ file); VC4 is also an abbreviation used to refer to the Visual C++ 4 program.
Program(s) that open vc4 files	Windows: Microsoft Visual C++; Editable with a text editor

Information from FileInfo.com - The File Extensions Resource.
http://www.fileinfo.com/extension/vc4