it is possible, but not in that said configuration. you can run as many as you want as long as you have room for them, however they won't actually all be combined to work as one. you can however get a specially designed motherboard that supports technologies such as sli and crossfire which are built to have multiple GPUs
I agree with all the above posts. If you have an agp slot and a pci slot, you will want to use the apg slot for a graphics card. Unless of course, it is a pci express slot. Because then you would want to use that one for a single graphics card. Hope this helps..
YES, if you can find two Voodoo 2's or 3's one in either flavour and then dig up some really old drivers from the interwibble, also a vga connector lead would be required, I used the one from my 4MB Orchid 3DFX accelarator card but you might find those a little hard to find these days.
More to the point, why would you want to run a pci & an agp card together?