How can I configure dual headphones under Windows 7?

I have a similar laptop (studio 17), and it has two headphone jacks also. Currently running Vista, I can stream audio to both headphone jacks/devices. Try updated drivers from Dell, especially the IDT Audio Control Panel Driver...I have no problems, and it didn't require any set up...Is your machine an upgrade from Vista?

Try updating your audio drivers; on some laptops it appears to be represented as a single device.

What kind of audio hardware is in the laptop? Any device ID or driver version may help locate a fix for your problem. However I would see if newer drivers for Windows 7 for your audio device exist that may correct the problem right away.

Is there something special ... to allow both headphones to operate simultaneously?

A Speaker and Headphone Splitter lets you connect two stereo headphones or speakers to the same mini-stereo jack.

Of course, if you're skilled with a soldering iron, you may disconnect the 2nd jack and split the connection of the 1st jack internally. :)