How to open a .dat file?

I'm wondering if there's a way to open the settings.dat file and make tweaks or optimizations to the graphics engine for improved frame rates. I have a intel mobile 4 series graphics chipset on Windows Vista 64-bit and its a little choppy.

A hex editor.

To that end, HxD is a good freeware Hex Editor.

Is this really possible? I mean tweak graphic engines?