Memory question

[Ropes4u]

I am upgrading an older pc so I can run mastercam on it. It has a 2.4c, IS7 and 2 sticks of 256mb of PC3200 Corsair XMS. Should I get 2 more of those sticks or can I run another gig of corsair xms along with the old sticks.

Thanks, John

forgive any idiocy I was up all night..