Your pc probably has integrated graphics,and yes you would need a graphics processor to play any n64 games.Your comp may only have pci slots but your comp is way too slow to bother playing any newer pc games.if your just gonna play n64 games and some older pc games get a geforce4mc pci card as that would do just fine.
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new pc=pentiumd 820 dualcore,250gb sata hdd,intel gma 950,19 inch lcd,lexmark printer,8in1 media card reader.
laptop=hp pavilion dv51099nr
core2 duot 5800,500gb wd 5400rpm hdd,512mb nvidia9600gt mobile gfxcard,15.4 inch 1280x800 screen,8x dvd burner.