External Display Resolution

I'm trying to connect my Sony LCD TV to my Acer Aspire 5570Z using a VGA cable. The laptop is using the Intel 645GM graphics chipset.

When I connect up, the display clone works, but I am unable to set the external display to the Tv's native resolution (1366x768). That resolution doesn't even show up as an option. Also, the external display doesn't actually display the desktop at a different resolution, it simply stretches/shrinks/crops the image of the laptop display to fit into the resolution of the TV.

Any help would be appreciated.