When installing dual graphics cards must they be identical?

I have one card and want to use it in a barebones kit, but the included card is not the same. They are both 256 megs.

When installing dual graphics cards must they be identical?
2 graphics cards of the same model that do not support SLI will conflict each other and cause headaches, this means the cards must be SLI and your MOBO must also be SLI compatible.
Reply:if they are both 256 why change it? Unless the card you want to install has different connectors theres really no point.....but if you want to install it you need to disable the onboard card as it will conflict with the agp or pci card.