In the PC version at least you cannot use a save game from your older version if you upgrade. There are quite a few differences in the upgrade that make them incompatible. You can opt to play the add-on Flames of Vengeance with your character that completes DKS, or start a new charachter which will not have any of the equipment of your old one. Played it both ways and both have their good points. I've found the level of replay with this game very high and it is cetainly a great bargain!
