try downloading and installing this power management suite from dell. I know it says for vista but it will work for Win7 as well. Reboot after install and let me know if it works. Drivers and Downloads
running the latest bios? have you tried popping in your windows disc and running sfc /scannow by type in "sfc /scannow" into search box and hitting enter?
I decided to update my video driver to a more updated version found on laptopvideo2go and that seems to have fixed my problem. Thanks for the help anyway.