I'm not sure, but I think I know what your problem is. I notice while playing the demo, it's like the "dark side" was suddenly COMPLETELY black. I'm not sure what caused the change, but it's still there even after increasing brightness and contrast (monitor) as well as the in-game gamma settings.

If that is the problem then you're not alone. As well as that there was a slight color improvement, and I thought it was part of this mysterious change...but I just remembered I changed the color settings in my monitor.

Actualy my problem is that EVERYTHING is too dark, my monitor's brightness is set to max (it's naturally dark and a very crappy monitor) and I've tried everything from adjusting the Desktop brightness as well as using Adobe Gamma to adjust it. These methods I've used to adjust the gamma on my screen many times before however won't work now. I was wondering if anyone else had a solution.

Bust out $100 and buy a new monitor? You said your self the your monitor is naturally dark and crappy. I don't think it's gonna get any better.