screenshots have worked very well through most all versions of mame, the problem is usually you aren't looking in the right directory (or have the right directory the screenshots are created from) mame32 esepcially has put images in a moving target, here are the directories i will sugest creating to get the F12 to work in them.(posted 8969 days ago)images
pcx
gif
bmp
snap
i can't remember which version goes to which directory but usually they'll end up in there, there are only a few games where F12 is broken for, which game are you trying to snap?