I just installed Win 10 64 bits. It sucks Anyway, when I double click a JPG file to view it in Irfan I get this error "Error executing program! (31)" from Total Commander. It works if I drag/drop the jpg file over Irfan icon (in TCMD toolbar).
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I use:
TCMD 8.52a 64bits
Win 10 64 bits (activated)
Solved by running Irfan as admin so it could correctly associate itself with image files. Strange that before doing this, double clicking a jpg file in Total Commander didn't worked, but in WinExplorer worked (even though the file was open not in Irfan but in MSPaint).
This error 31 means that one program (Total Commander?) was running as Administrator, and the other program (Irfanview) was also already running, but as a normal user. Due to the account protection, DDE (dynamic data exchange) between the two will be blocked. You need to close Irfanview if you opened it from Explorer (running as normal user) and then want to use it from Total Commander if it is run as administrator.
I had the same error (Windows 10 x64).
I set IrfanView as default photo viewer in Windows Control Panel (Control Panel=>Default Programs=>Photo Viewer=>Irfan View) and it helped. IrfanView has small message in Properties/Settings=>Extensions "If Win 10 warrnings, please use the sytem control panel" but I didn't notice it at first time.
I hope it will be useful for someone