No program supports R2D files.
The file origin is unknown.
It is probably infected.
The file may propagate the virus.
Follow the instructions in the antivirus software to prevent spreading. The file could be incomplete or corrupted.
It may fail to open.
R2D files store Reflex database data.
They use a flat text format, similar to .RDX files.
Reflex ran on DOS PCs.
It is now obsolete.
Spreadsheets could open R2D files.
Modern software cannot.
Try opening the file in a spreadsheet.
Rename it .TXT first.
RISA-2D opens .R2D files in Windows.
Mobile devices may not support R2D files properly.
R2D file issues can often be fixed.
The filename extension may be typed wrong.
Check it is R2D.
If that is correct, update the software you use to open them.
Only the newest versions work.
Scan for viruses with antivirus software too.
If it still does not open, install RISA-2D.
That should fix issues opening R2D files.