I installed MAME4ALL today, for some reason it doesn't show up in either GUI, but the documentation does on the Desktop GUI. I tried downloadign Beta7 from several sources, but they are all the same.
If not showing please delete mame4all from appdata and also you might have problem with your pnd and delete that also.
Make sure you have roms in rom folder.
Isn't better if you used mame ex which uses the latest build than other mame emulator on pandora plus it has better compatibility and plays more games.
you need to check what firmware version you have - with HF6 some new tokens were introduced within the .pnd stuff older ones don't understand. so you need to update to HF6 to get them into the menu and such.
I find quite a few times that downloads show as completed when using the Pandora but when you compare the size of the file with the one on the repo there is a difference.
Downloading a 2nd time and overwriting the 1st file usually fixes the problem.
Seriously though any time this happens it is almost invariably 99.999999999% of the time is a corrupted PND. You don't need to delete your appdata or anything like that.
If you still having still problem try different fw like super zaxxon 1.5 beta 1.1 it's very stable and doesn't give any issues by using this fw your problem should be solved.