Howdy there!
OK, as far as mess goes, heres a few things to make sure you have right... make sure the 7800 bios is in the folder marked "bios" also make sure that the 7800 bios is ZIPPED! If you unzip it , things dont like to work.
Once you make sure that thats where its supposed to be, go to the main screen of mess and right click on a7800... go to properties, then go to audit... click audit and see what hapens, it should say "passed" if thats ok, then click on software. You dont actually have to have the 7800 roms in the same folder marked software if you dont wat... i too have lots of emus that share roms. Just select browse after you click on software and tell the mess where your roms are. Either that or create a folder in the software folder in mess marked a7800 and transfer all the roms there.
Ok, once you have the bios set up and it passes the check, and you have it recognizing where the software is, all you should have to do is go tot eh main screen on mess, select a7800... the games shoud all show up in the window makrked software. if they do, just click on whatever game you want to play, and you should be good to go.
mess is 99% like mame, so if you go that to work, i dont see why you shouldnt be able to get mess to work.
As a last resort i might be able to send you my mess folders that are already set up.
let me know if any of this works for you!
As far as how things are here... well to tell the truth they suck! LOL Its very hot and humid... temps inthe high 90s to low 100s... humidity around 75 - 85% in other words pretty darn miserable! Unless of course ya like to sweat!