Use your DVD and then let windows7 update, it will find if there are updated drivers for your hardware.
I know I have to use my DVD, but Dell's systems are kinda weird. I am not sure which one to install first then the next. I don't really get the instructions on the Dell's website "Installing Drivers in the Correct Order". Its this link: http://support.dell.com/support/topics/global.aspx/support/kcs/document?docid=268873&doclang=en?c=us&l=en&s=dhs&cs=19