Reference note from Autodesk product Manager Irvin Hayes
"
Mike,
I did some digging and just as you have experienced Vault Explorer is designed to open the latest version of AutoCAD when you double-click on a DWG file.
If the latest version of AutoCAD is not installed, it will go to the Windows file associations to let whatever program that is configured to open the file. Currently there is now way to change this behavior."
We would like Vault Explorer to always recognize the Windows File Association setting to determine which AutoCAD version to launch when doubleclicking a DWG in Vault Explorer. Regardless of which versions of AutoCAD are installed.