delete everything on the hard drive.
you can't run 2 different cards at the same time, as it wont work, as if they are agp, then there isnt enough slots for them in the first place. and if it was pci, than the pc would choose one over the other, and with PCI express, you have two of the same cards, so it would work.
leaving the drivers on woud cause clashes with the new ones.
Cisco CCNA, Comptia A+, 1/3 through CCNP