Don't bother trying to rename the snapshots to match your rom names!! Trust me, it is much harder and will take longer! As Lustar said above, all you need to do is use the goodTools program for the specific sets you have (ie. use GoodNES for NES, GoodSNES for SNES) to rename your roms to match the snapshots. This will rename all your roms to the goodtools format, e.g. with (U) [!] etc.. They will then match all of the screenshots exactly.