He's wanting the monitors to be treated as if they were one big monitor to the OS, so that programs see a 3200x1200 screen instead of two 1600x1200 screens. In OS X, the menubar would be spanning both screens and such.
Generally on Windows, video drivers offer this as an option above and beyond mirroring and dual monitor option. Offhand, I'm not sure how to do this with an 8800 under OS X.