How do u get 64 color bit?

I have a NVidia geforce 8600 card and i have only 32 bit. PLz help.

are you saying the option of 16 or 32 when you go into display settings in windows? it dosnt go higher than that dude.

even with 64 bit vista and tri sli gtx 280's it dosnt go higher, because windows only goes that high. but in games of course it takes full advantage.