if this is an iMac from 1999 it should be a G3 with probably the slot loading optical drive. If that is the case, this does not have a changable video card in it anyways. These computers are not worth putting any money into at this point since you can get much more powerful G4 computers, such as a dual 533, for very little green. Granted, they still will not be any screaming machine by today's standards, but they would certainly still be a good step up from that G3 imac.