Hello,
Set up your speaker’s configuration and see if it helps.
a. Open Audio Devices and Sound Themes by clicking the Start button, clicking Control Panel, clicking Sound
b. Click the Playback tab, select Speakers, and then click Configure.c. Under Audio Channels, select 5.1 Surround and click Test. You should hear a tone play in each speaker
d. Click Next, and then follow the directions to continue the configuration process.
http://windows.microsoft.com/en-GB/windows7/Sound-cards-frequently-asked-questions
Hope this information helps.