Thanks for the reply. I am still in the cabinet building stage of this project and wanted to get a head start on the software side of it and kinda jumped the gun... so I was messing around and figured out that I didn't need irotate for the vertical monitor when all I had to do was change it 90 degrees in the nvidia settings, and as far as mame sending the game to a particular screen.. I guess the question I really wanted to know was if it was possible to do it in the the mame ini because I already knew about multi-monitor support and artwork, why not specific games?
I still wonder if it is somehow possible in mame. That would make life easier.
Badmouth I did not know MAMEUI could do that! So when all fails I will give it a try. thx!
YOU DO NOT NEED TO ROTATE THE WINDOWS DESKTOP USING ANY METHOD!!!!!!!!!!!!

MAME and every other emulator will display it correctly without doing that.
In fact, rotating the desktop will screw things up.
Look at the rotation options in mame.ini
Play around with them and learn what they do.
Disabling rotation alltogether is what you want.
Not rotated=sideways on a horizontal monitor (which from what I understand, you are going to physically mount vertically)
There may be individual games that had the monitor turned right instead of left, etc, so they will be upside down.
Just hit TAB while in game, select video options and select 180 degrees for the rotation.
I don't know if you'll make it that far, but when you get into some of the oddball emulators that have no rotation options,
the left side of the horizontal screen should be the bottom if mounted vertically.
So I'd recommend going ahead and mounting it that way.