Open With always starts new instance

[mccracken.matt]

I recently got a new computer and set up all of my file associations.
When I double click to open a file, I always get a new instance of the
application rather than using an existing instance of the application
that is already running. For example, i have several file type
pointing to visual studio, and when I open a file, I get a brand new
instance of VS instead of just opening a new tab within the currently
running instance's editor. Obviously, this isn't desirable behavior.

My old laptop opens the items in an instance that is already running,
so I'm thinking that there is a setting somewhere that is causing this
behavior. I've looked all over for a setting that would fix it, but
I'm at a loss.

Any ideas?

 

[Guest]

"Launch folder windows in a new process" is in My Computer/tools
menu/options/View tab/see checkbox. I would guess M.exe is responding to an
explorer setting.

If not, it would be likely to be a VS *.INI