for computer 1 with no video you could try setting switchres 0 in mame.ini
nvidia/ati cards:
i dont use nvidia so cant recommend one, but for ati, these below:
ATI Radeon 7000, 7200, 7500, 8500, 9000, 9100,
9200, 9250, 9500, 9550, 9600, 9700,
9800, X300, X550, X600, X700, X800,
X850, X1300, X1600, X1800, X1900,
X1950, ArcadeVGA 9200/9250,
9500, 9550, 9600, 9700, 9800, X300,
X550, X600, X700, X740, X800, X850,
X1050, X1200, X1300, X1550, X1600,
X1650, X1800, X1900, X1950, HD 2350,
HD 2400, HD 2600, HD 2900, HD 3200,
HD 3300, HD 3400, HD 3410, HD 3450,
HD 3550, HD 3570, HD 3600, HD 3610,
HD 3690, HD 3730, HD 3750, HD 3800,
HD 3830, HD 3850, HD 3870, HD 4230,
HD 4250, HD 4350, HD 4550, HD 4570,
HD 4580, HD 4650, HD 4670, HD 4730,
HD 4750, HD 4800, HD 4850, HD 4870,
HD 4890
added note: doesn't really apply to your needs, but anyway fyi Calamity of Groovymame states that for best results (ie. the ability to handle a wide range of custom modes/resolutions), get a Radeon 9250 (AGP), Radeon X300-X600 (PCIe), or Radeon HD 4xxx (PCIe)