|If the sound on your system is on board (i.e. on the motherboard) then your system CD that came with it will have the drivers on it. |
If your sound is from an add on card, then that card will have a driver CD that came with it, or if it was an OEM supplied PC then the system disc will have drivers on it too.
Either way you need to install the sound drivers before your sound will work.
If you pop your CD in your optical drive it may auto detect and throw up the menu with a list of drivers to install.
Seeing as you have not done this it is also possible you may not have installed other drivers such as the chip set drivers which make your system run better than the native OS drivers.
So check the CD for other drivers and make sure that you have installed them too.
☺ When everything else fails, read the instructions.