What is 001 file?

.001 file is a backup of the hard disk created from Norton Ghost. When the file size of the backup exceeds the size limit as 2 GB in DOS, the backup will split into multiple files. The first separated file is .001 file, while other parts of the separated backup have extensions as “.002”, “.003”, etc. Separate backups also include a .GHO file which contains information necessary for the restoring the file.