Actually I'm using a Horizontal monitor only, so I need to be able to make all rotated game to show horizontally. It will take to long to change each game from "R" to "H" manually. Ugh
My first cabinet had a stationary horizontal monitor (I've only used vertical monitors in cocktail cabs since), and as I recall it played both horizontal and vertical games no problem, with ArcadeOS straight out of the box. I sold the machine a while ago, so I can't be sure what the default settings were, but...
in arcadeos.cfg you will find these two lines:
#auto rotate games, left/right
autorotate=1you want to change it to
autorotate=0by default, it's set to 0, but maybe you changed it along the way somewhere?
If this doesn't help you, maybe you should try asking on the mameworld.com ArcadeOS message board, there's a bunch of ArcadeOS experts there, including LasVegas who is currently in charge of ArcadeOS development.