You should make sure all your drivers are up to date before even starting to try to solve a problem that might be already solved by an update.
This link might help.
http://www.ma-config.com/en/home/
It automatically searches for the latest drivers updates for your hardware and offers to download.
You might want to have a look at Dell Support Center
http://support.dell.com/support/topics/global.aspx/support/product_support/product_support_central?c=us&cs=19&l=en&s=dhs&~ck=mn
I would have gone the extra mile, but you need to provide more information if you want more help.
Usually a good start is:
* Hardware Model Details
* Operating System
* When was the last time it was working
* When did you notice it started not working
* What were you doing
* Any info you think can be useful
Hope it helps.
Cédric