I have also a problem on windows gui. Can not run "-bios 1" or "-bios T1" = NASBUG1.T1 (original version) "-bios 2" or "-bios T2" = NASBUG1.T2 (1978) Even I select in Properties - Miscellanous - Bios - NasBug T1 or Nasbug T2 If i start the emulation it show me always Nasbug T4 (NASBUG 4). The only way to start the right Bios is to run on command line. As example: mess.exe nascom1 -bios T2
This is because MAMEUI writes the full descriptive name of the BIOS to <system>.ini instead of the short name.