It appears that you have no driver for your sound system in your operating system. If you have the cds, reinstall your drivers. If not, Search on the net for drivers for the motherboard. Your sound is on the motherboard, thus you will need the mother board drivers and sometimes software for installation.
Something may have happened to knock out the drivers. Reinstalling may fix the problems.
Answers & Comments
It appears that you have no driver for your sound system in your operating system.
If you have the cds, reinstall your drivers.
If not,
Search on the net for drivers for the motherboard.
Your sound is on the motherboard, thus you will need the mother board drivers and sometimes software for installation.
Something may have happened to knock out the drivers. Reinstalling may fix the problems.