MAME4droid (0.139u1) uses game ROMs from the MAME '0.139' ROM set (August 2010). Note: This is different than the ROMs used in MAME4droid (0.37b5). These ROMs cannot be used interchangeably.
ROMs should be placed in the "roms" folder of your MAME4droid installation folder. In a default install of MAME4droid, this path is /sdcard/MAME4droid/roms
ROMs may be stored anywhere you like, but you'll need to change the path located under Options->Settings->General->Change ROMs path
Note: File and directory names are case-sensitive. MRDO.ZIP is not the same as mrdo.zip. Always use ZIPped ROMs with filenames in lower case..
Some games' sound is not perfectly emulated by MAME. Therefore, digital sound files (known as samples) are used to complete the sound for these games.
These should be placed in the samples folder within your MAME4droid installation; ZIPped and lower case filename (i.e. startrek.zip) In a default install of MAME4droid, this path is /sdcard/MAME4droid/samples