Notes about the D2I file extension:
Incorrect file associations could be the result of underlying issues within your PC system. As such it is highly recommended to scan your PC for invalid registry entries, unused processes and other unfavourable system settings to identify slowdown issues.
The D2I file type is primarily associated with 'Diablo II'. ATMA is a Single Player muling program for Diablo II by Hakai_no_Tenshi. It stands for "A Tenshi Muling Application" and is designed to let you organize and categorize your Diablo II characters, mules and items. The .D2I file is not used by the game; it is a storage file for items.