MAME trouble

[kezune]

For a long time I couldn't work out how to get Samurai Showdown to work on MAME until I realised I needed the neo geo bios in the roms folder. Now all my other roms work fine and I have the latest version of MAME but when I try to run samurai showdown or SNK vs Capcom it loads up all the files then the screen goes black for an instant (as if it were just about to start) then it just goes back to the desktop and nothing happens.

Any help would be greatly appreciated :D