Monitor issues Dell Inspiron 1521

I have a Dell Inspiron 1521. Windows vista home basic 16-bit

Upon powering up, the screen is bright all the way up to the windows login screen. The screen does this whether the laptop is plugged in or not. when it gets to windows login, the screen goes so dark i can barely see the screen. (like 1% brightness) I have to hold it in the light just right to see it.

If I plug in an external monitor, the external monitor shows me the display just fine and occasionally, the screen on the laptop will go back to full brightness (with the external monitor plugged in).

I have checked all power settings in both windows and the catalyst control center and everything seem to be in order (at 100% brightness).

Any ideas on what's going on?

The only other thing I can think of is to backup all data and format the hard drive to hard-reset all settings but, I hope it dosen't come to that.

Thanks
-Abush1707

I've done some research to find this hotkey to no avale.

any idea what the hotkey is?
from what i've read, it may be Fn+Fkey (F1, F10, etc.). Just not sure which Fkey. i'm gonna try a few.