Nikon D40 over & under Exposure problem?

I have just bought a Nikon D40 and after playing with it for a while I realised there's a big problem with it. It overexposes and underexposes at the same time in the same picture. Just like when you would shoot high contrast photos. Compared with D90 looks just wrong.

Any help or advice? Many thanks

Added (1). I know D40 tends to overexpose and I know how to overcompensate it. Trouble it that now all pictures look wrong, like on forced high contrast. Just like shooting out of the window and catching some of the room too, only the pictures are all taken outdoors. Just plain wrong.

That's impossible. You can't over and under expose in the same frame - the aperture is set to one place… Dead on, over or under - never two in one shot.

If the contrast is too high and you have an owner's manual, check the menu to adjust the comtrast.
If you don't have a manual check the Nikon site - you can download a pdf version there.

This lengthy article will teach you to be an expert on the Nikon D40's controls… The D40 does a great job so long as you preset the exposure compensation to -0.7… AF-C and AF-S. These are explained under Focus Modes. METERING