What is .dat_old file?
The ".dat_old" files is used by the backup file created by Minecraft, an open-ended 3D world construction game. The file saves a backup of the level.dat file, which is used for saving maps that use Minecraft's Alpha level format. The *dat_old file is used as a restore point in case the level.dat file becomes corrupted.
Recommended Software Programs to open .dat_old file