Barnes and Nobel’s new e-book reader has just hit stores and already the hackers are looking for new uses for it.

Wired reports that some hackers have already found a way to run the Pandora music software in the background of the device.

“It wasn’t that hard,” says Robbie Trencheny, a 18-year-old student who is also the team leader at nookDevs, a wiki and an online forum for Nook enthusiasts. “Once we had rooted the Nook (on Sunday), it was only a matter of time until we could put an app on it.”

“Rooting” the Nook involves hacking its system files to get full access to the device’s Android operating system. But unlike jailbreaking the iPhone, rooting the Nook isn’t just about tinkering with the software. Instead, Nook customers have to take a screwdriver to get to the device’s innards. Nook’s Android OS is on a microSD card that needs to be connected to a computer to change a file on it. Once that’s done, the power of Nook’s Android OS is available to its users.

To run Pandora, Trencheny first searched for the .apk file associated with the app. “It’s a file extension that Android uses and every app has it,” he says. Once that file is wirelessly downloaded onto the 3G-enabled Nook, users have to run a command in the terminal shell of the device. With a few more steps described on the nookDevs wiki, they can get the software installed.

There are a few more steps to get it operational. The Nook’s touchscreen won’t cooperate with the Pandora app so users have to use a VNC remote control software to get past the app’s initial login screen. Once that’s done, Pandora works perfectly with the Nook touchscreen and can run in the background as you browse books, says Trencheny.

NookDevs members haven’t heard any complaint, so far, from Barnes & Noble. “We have looked through the end user license agreement and, as far we can tell, there is nothing in there to get us into trouble,” says Trencheny. “We are not abusing the 3G or breaking the DRM rights on the books.”