hit the start button in windows, the choose run
type cmd then hit enter
im assuming you know a bit of dos commands so change your directory to your roms
once your there you can type del *(j)*.* then hit enter
what that does is delete all your japanese roms
again im gonna assume your roms are named like mines are for example afterburner 2 is named After Burner II (U) [!]
that (u) means its a usa game, the (j) means its a japanese game, and i think (e) is the euro game and (g) is german. need any help msg me