Actually it's every table I have at the moment. I was testing hat you said last night on the adam's family and elvira scared stiff. I right click enable board, move the vpinmeme dmd window to the the back glass and resize it and right click uncheck board. Exit the table, exit everything else. Load everything back up and the dmd is back on the playing field monitor. every table except the ones that have it built into the back glass will do this each time. both in the global and F1 setting cabinet modes are clicked.
Download Freezys DMD Extensions
Unzip that into your VpinMAME folder
Run a table, lets say adams family
hit F1 (and VPX should be NOT in exclusive full screen or you wont see the dialogs)
uncheck show DMD
check use external DLL
click ok
now exit and relaunch table (F3 does not always properly re-init every table)
A DMD window should appear, that you can click and drag around and has a resize handle on the bottom right
Move it to your DMD screen, size it as needed
Now right click it
Pick to save global
Now right click it again
Pick to save position for game name
Why twice?
Saving globally because
So that every DMD will at least start on the backglass screen, even is the size/shape does not match, since not all backglasses use a standard sized DMD area
Saving for gamename
So that the exact size and shape for that exact table is remembered, cause the DMD location and size for apollo 13 aint the same as for AC DC, unless you have a 3 screen cab
in which case Most DMD's will be the same (but a few will not, like the apollo 13 3 screen backglass)
PS
If you do not have it, you should also have flexDMD installed
it also unzips into the vpinmame folder
and then you just run flexdmdui and click the 2 register buttons