Why would you use XP for that?
Your SCREAMING dos boot... then add that to the autoexec.bat. MUCH FASTER boot... MUCH cheaper... SDD (sci display doctor) is now free so you will be able to get native resolutions almost for sure..
My guess would be lack of DOS drivers for his hardware, but otherwise I agree with you.
But for XP. Just create a shortcut for mame that launches pacman... And add it to the startup.
He did that, He want's to hide the Dos Box. - Hmmmn, it can be done - It came up recently b/c Ciro wanted to hide it in EmuLoader and he got it to work (But I think he wrote a Delph component specifically for it). I know Mamewah can hide it as well.
What you might be able to do is create MAMEwah with a totally black skin and then use some kind of auto-it or macrokey program to launch pacman from MAMEwah, but there needs to be a better way -
BTW, you might get better results by renaming the thread "Hiding DOS box on MAME startup". You also might do a forum search on that.