A good computer to run the simulators?
you probably can upgrade no probs.
Take off the side of the case, if you see a brown slot in the middle of the motherboard (under the CPU) then its an AGP slot.
If you don't see it, and only white pci slots exist, then you gotta find a PCI card.
You disable on-board graphics in the Bios, not in device manager.
SimJen