what menu are you referring to?
HAve you read the pc2jamma page?
Have you checked out hte excellent info at
http://how.to/mame ?
It sounds like you are mixing up stuff a bit... which is easy to do with all the different hz and khz bantared about regarding monitors... anyways you need to get that video card outputting 15khz... either by using arcadeos's built in driver, or arcmon TSR, or configuring Advance MAme properly...
either way be careful! don't send full VGA screens to your arcade monitor (i.e. your POST screens and DOS... etc...) you ARE in DOS right?
*Shrug*
Rampy