|I'm pretty sure it can be. With the secondary monitor plugged in to the laptop, press and hold the FN (function) key. While holding the FN key, find the Numeric key with the monitor emblem on it and hit it. This should cycle through several options. External Monitor only, Laptop Monitor only, and finally, both monitors in a dual monitor setup.|
Once you have the dual configured, you'll likely have to access the display software to have it stretch the display across both monitors. This will give you one big desktop as compared to two copies of the same thing.