File created by Indexing Service, a software component of the Windows (operating system|operating system) that creates a searchable file system index from files on the hard drive; contains data that helps Windows perform quicker searches.
000 files are saved with several other types of files that make up the search index. Other types may include .BK1, .BK2, .FID, .HSH, .PS1, and .PS2 files.
The Indexing Service search index is often created in the following directory: C:\System Volume Information\catalog.wci\. The index may also be generated for external volumes connected to the Windows computer, such as flash drives.
File archive compressed by Microsoft DoubleSpace, an older file compression utility included with MS-DOS; can be decompressed and opened on the fly using MS-DOS with the DBLSPACE.BIN compression subsystem installed.
Disc image data file created by Virtual CD, a disc imaging program; created by versions 4 and later of the software; contains the data for the disc and is saved alongside a .VC4 file; may also be saved with a .VCX file, which is the CD Editor project that was used to create the 000 and VC4 files.
000 files can be burned to a disc using Virtual CD. However, you need to open the corresponding VC4 file (or VCX file if it exists), which then allows the Virtual CD software to access the disc image.