help with a "Uno" board with an AT Mega 8A-PU processor

I am trying to load the Blink example onto a supposedly Uno V3 board with at AT Mega 8A-PU processor. Windows recognises the board on COM3, and can communicate with it. When I try to compile and load the Blink program I get the message:-

Wrong microcontroller found - did you select the right board from the Tools > Boards menu

This is the correct message as I have the wrong processor on the board - any idea how to configure the ide to talk to this board/microcontroller combination?

search for datasheet..
bootloader ?
info for the chip must be in the boards-file (if its not present already, supplier of card should provide this info)