try going to control panel, open the multimedia configurations. on the first panel on the bottom is a checkbox to place the sound icon on your taskbar.
also on the first tab you can see your playback devices, make sure yours is listed, there should be a drop down menu to select your audio device.
is it an actual sound card or onboard chipset? i have seen some soundblaster cards act up and the workable solution was to remove them from their pci slot on the motherboard, and slide it into a new slot, reinstall drivers etc ...