Hello. The only possible option you have on that model is the HDMI port. If the receiver of your theater system has that type of port you can connect the laptop to it and see if the laptop recognizes the receiver and will send it audio. If it will then you should be able to have surround sound when you are playing source material that has surround channels, such as a dvd movie.
If you want to buy additional hardware look for a usb sound card that that output ports that match up with whatever your theater system has.
Jim Coates -- 15 years on the Dell Laptop Audio boards -- since 2/6/04