Not able to dim display either with Fn keys or through power options.

Please bare with me, I'm new to this but:

I have a Dell XPS 15 running 7 x64 (more details please see my page) and I am trying to dim my display through the OS. When I press the Fn keys to change the display brightness, the notification shows on screen that it is changing the brightness with a nice little slider and all, but nothing moves and the brightness won't change. I've tried pressing repeatedly, holding down, no change. So naturally, the next step is to change the display brightness settings in power options. Only problem is, IT'S NOT THERE! I have no option relating to display brightness. I've tried re-installing display driver with no help. I don't know if it is a problem with Dell's display not supporting the function or with Windows 7 not offering.

Thanks in advance for any help, please ask if any more info is needed.
Dusty

As I stated above, I have already tried re-installing drivers. No change.

Thanks for the help all but it seems that a VPN/Remote Desktop Connection program I have installed which has its own display driver replaced my default display driver which removed this function. Once uninstalled through advanced options, the display IMMEDIATELY regained the brightness change function. I found the solution here:

Cannot change screen brightness through hotkeys or any other method - Microsoft Answers

Thanks again for everyone's help,
Dusty