BG2 natively supports 1024x768. You really don't need the widescreen mod for BG2 -- put the screen any larger, and the text, dialogs, and sprites are just far too small. Try it at that resolution first, see how you like it.
yes but it doesn't allow me to change the rez and I really wana play just not in the left hand corner
You don't change the resolution in-game. Make sure the game is not running and open Windows Explorer to the folder where Baldur's Gate II is installed (where BGMain.exe is) and run BGConfig.exe. Go down to Graphics >> Display and confirm 'Yes' when it prompts. Check the 'Unlock Modes' and put a checkmark in 1024x768. I would not use any of the others, if I were you, because they're really awful like I said before.