What game list are you talking about?
This one?: (btw, that ugly thing was only put there to keep noobs who don't read instructions from complaining that nothing happened when they clicked mame.exe)

If it doesn't look like that, you are using a UI version of MAME (MAMEUI, MAME32, MAMEPlus) or a front-end(Mala, Hyperspin, Mamewah)
Always mention what software you're using when asking for help.
A lot of front-ends have an option to hide bios roms.
The answer is different depending on which one you're using.