Go to control panel, double click add/remove programs,
when the program comes up on screen, click on windows setup, scroll down to multimedia, highlight multimedia and click on details, make sure the volume control option is checked, click OK, OK and after you get back to your desktop, restart your computer. then see if the volume control option in sounds is working now, if it is click on show volume control on task bar. You may have to restart the computer again to make it show up.
Hope this helps.