Optiplex 980 sound plays both internal/external

[kleis]

With the Dell Optiplex 980, I am not able to separate the sound from internal speaker from my external speakers and they are just a general Creative 2.1 speakers and uses a separate remote for volume. However, the internal speaker volume is on the sys tray or next to the clock in the typical Win. 7 Pro desktop where cliking the icon speaker adjusts volume. Even though I have sound control manager that is Realtek's built-in, it doesn't separate or there's no kill off switch or entry to close off the internal speaker. Also, since I purchased this computer I wasn't aware that it's more for business and less consumer so, I indeed like sound and music and vidoes, so it could have been a slightly wrong choice. Should I add a sound card to the motherboard to enhance or improve sound quality overall?

 

[Cycloid Torus]

The link tells how to enable sound device - reverse it and disable what you choose.
http://www.computerhope.com/issues/ch001195.htm