Well, the first three things you should try are....
1. Audit your games within the MAME emulator you are using.
2. Audit your games with an external programme like Romcenter or Clrmamepro.
3. Your files are probably outdated, so go to a site that updates their ROMs & BIOS files regularly and download the stuff you need. *Because you legally own the originals, don't you?*