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In my office, we use a custom right-click menu in .dwg files to allow the users to choose which version of AutoCAD they want to open the file.

It howover requires that AutoCAD don't mess with the file association of DWG files, otherwise the custom menu is lost.

Once the menu is installed, the first time AutoCAD is open it detects it is not the default DWG launcher and asks:

I choose "Do not associate DWG files with AutoCAD", to preserve the right-click menu configuration.

Howover, I'm having an issue with a workstation where this window is not popping up, and it is reassociating DWG files with AutoCAD, what ruins the whole thing.

Is there some way I can reset this setting and make it ask again or simply configure this behaviour somewhere?

I managed to workaround the problem, and even have a better handling of .dwg files behaviour by changing the way I install the file association.

Instead of modifying HKEY_CLASSES_ROOT.dwg, I just leave that alone and modify HKEY_CURRENT_USERSoftwareMicrosoftWindowsCurrentVersionExplorerFileExts.dwgUserChoice instead.

This overrides the default association for .dwg files, and AutoCAD won't even bother.

If anyone is curious, this is what I'm doing:

AutoCAD_2006_2014.reg

Windows Registry Editor Version 5.00



[-HKEY_CURRENT_USERSoftwareMicrosoftWindowsCurrentVersionExplorerFileExts.dwg]



[-HKEY_CLASSES_ROOTAutoCAD.Drawing.Multi]



[HKEY_CURRENT_USERSoftwareMicrosoftWindowsCurrentVersionExplorerFileExts.dwgUserChoice]

"Progid"="AutoCAD.Drawing.Multi"



[HKEY_CLASSES_ROOTAutoCAD.Drawing.Multi]

@="Open with AutoCAD 2014 / 2006"



[HKEY_CLASSES_ROOTAutoCAD.Drawing.MultiDefaultIcon]

@="C:\Program Files\Autodesk\AutoCAD 2014\en-US\acadficn.dll,49"



[HKEY_CLASSES_ROOTAutoCAD.Drawing.Multishell]

@="Open_with_AutoCAD_2014"



[HKEY_CLASSES_ROOTAutoCAD.Drawing.MultishellOpen_with_AutoCAD_2006]

@="Open with AutoCAD 2006"



[HKEY_CLASSES_ROOTAutoCAD.Drawing.MultishellOpen_with_AutoCAD_2006command]

@=""C:\Program Files (x86)\AutoCAD 2006\acad.exe" "%1""



[HKEY_CLASSES_ROOTAutoCAD.Drawing.MultishellOpen_with_AutoCAD_2006ddeexec]

@="[open("%1")]"



[HKEY_CLASSES_ROOTAutoCAD.Drawing.MultishellOpen_with_AutoCAD_2006ddeexecApplication]

@="AutoCAD.r16.DDE"



[HKEY_CLASSES_ROOTAutoCAD.Drawing.MultishellOpen_with_AutoCAD_2006ddeexecTopic]

@="System"



[HKEY_CLASSES_ROOTAutoCAD.Drawing.MultishellOpen_with_AutoCAD_2014]

@="Open with AutoCAD 2014"



[HKEY_CLASSES_ROOTAutoCAD.Drawing.MultishellOpen_with_AutoCAD_2014command]

@=""C:\Program Files\Autodesk\AutoCAD 2014\acad.exe" "%1""



[HKEY_CLASSES_ROOTAutoCAD.Drawing.MultishellOpen_with_AutoCAD_2014ddeexec]

@="[open("%1")]"



[HKEY_CLASSES_ROOTAutoCAD.Drawing.MultishellOpen_with_AutoCAD_2014ddeexecApplication]

@="AutoCAD.r19.DDE"



[HKEY_CLASSES_ROOTAutoCAD.Drawing.MultishellOpen_with_AutoCAD_2014ddeexecTopic]

@="System"

This allows both AutoCAD 2006 and AutoCAD 2014 to coexist on the same system, AutoCAD 2014 being the default one, and you can right-click any .dwg file and open with AutoCAD 2006.

This was created because some of our architects are relutant to upgrade from AutoCAD 2006, and some of our scripts are only compatible with AutoCAD 2006.

This does not answer the fundamental question though, so I'm not accepting it as answer. How to reset the DWG association setting on AutoCAD remains a mystery.