Hi Cynos.
Maybe I can help you in something!!!
I have one question for you, why you uses ArcadeOs. For better achieves with your configuration try to use ADVMENU with ADVMAME.
Advmenu at the moment is still in development, ArcadeOS no.
Here you can find a great tutorial to run both programs, Advmame and Advmenu...(sorry, is in Spanish but you can translate it with the inets translators....and there's plenty of photos too....

)
http://www.forumcommunity.net/?t=1265408In this tutorial, I explained every option and how to make the best performance with arcade monitors.
My config is very similar to yours:
PIV 2,4Ghz, Win98SE (without GUI), Ms-Dos, AVGA (Ati 7000 based...take care with it....AVGA 9X series seems not to work OK.), Advmame (0.99) and Advmenu..(the last version)
Cheers.