You have the Monitor and sound plugged into  the wrong colored-coded intake plug in back of your computer.

Take your computer to a local computer store and have the trusted Tech set your computer up correctly.  A FRIEND with experience can do the same thing.

Good Luck.

p.s.  I had the same problemSound CARD color codes
http://www.hobby-hour.com/electronics/sound-card-color-code.php






Almost all sound cards USE standard color codes for input/output connector JACKS.

 
In many cards, the microphone connector will be pink, the line out or headphone will be lime green, and the stereo line in will be light blue. Additional jacks may be present on newer soundcards for rear and mid SURROUND speakers.

There is a wildly accepted color standard for computer sound card input and output jacks, but connector colors may vary between different brands. If you think you have a nonstandard card, consult your soundcard's manual or the manufacturer's web site before making any connections.

Sound card color code: Color Connector
Lime Green Line-Out, Front Speakers, Headphones
Pink Microphone
Light Blue Stereo Line In
Orange Subwoofer and Center out
Black Rear Surround Speakers for 5.1 and 7.1 systems
Gray Middle Surround Speakers for 7.1 systems
Gold Midi / Game port (Joystick)