DA0 is an extension characteristic of files used in older Windows operating systems (95/98 / ME). DA0 are files where the system registry was backed up. Windows created these files automatically each time it was properly started. Files of this type can be the basis for repairing a damaged system registry. The registry is one of the most important elements of the system responsible for its correct operation.

A DA0 file is a backup of the original registry file with the DAT extension.