I'm trying to use dual monitors but every time I try to change the display settings(external monitor is on the right of the laptop, not the left etc...) my screens go black, then my laptop screen will come back "normally" but my external monitor will just flash different shades of red or black.

I cannot interact with anything on my laptop screen even though I can move my mouse around.
Even when the monitors attempt to revert back the external monitor continues to flicker instead of reverting.
The only way to stop it is to hard-boot but the new settings aren't saved. Also, when the dual monitors are both working my laptop screen has two vertical black bars along its sides.
It's like Natty just decided I couldn't use the outer inch and a half of my laptop
screen. My external monitor doesn't have this problem, and my laptop uses its full screen size when the external monitor is not hooked up. Does anyone know what I'm doing wrong?
I have an HP Pavillion dv7 and an HP w2338h external monitor. Thanks!