So what are these "shortcomings" of running a 64-bit OS. Driver support for what? Lightguns? So is that it, lightguns?
I run XP 64 and didn't have any problems getting drivers for my hardware. Running old hardware you might though.
64-bit OS's do run 32-bit software so I only see benefits. If your getting a new PC and a Dual Core or Quad Core it would seem silly not to get a 64-bit OS IMHO.
So is that it, lightguns?
Look at the 90's/Early 2000's era we're into for games being emulated in MAME.
Probably 1/3 of them are lightgun games. House Of The Dead 3, Area 51, Maximum Force, Beast Busters Second Nightmare, Carnevil, Crypt Killer, Confidential Mission, Evil Night, Ghost Squad, Gun Survivor, Gunblade NY, The Lost World, Operation Tiger, Police Trainer 1 and 2, Silent Scope series, Star Trek Voyager, Terraburst, Time Crisis series, Trophy Hunting, Turkey Hunting USA, Virtua Cop 3, World Combat.
You really looking to play those with a joystick or trackball?
