If it's telling you to enable sound in the BIOS it's probably detected onboard sound, but PCI Audio Device suggests that you've got a separate card.
Are you using onboard sound or a separate card? (A separate card will give you speaker connections towards the bottom of your PC (probably above or below your modem), onboard will give you the speaker connections on the thinner bit on the back where the mouse/keyboard plug in)
Work out which you're using, then you'll need to download the appropriate drivers. (Installation files will probably look for either onboard or separate sound)
click here download the personal edition and run it, look at the Audi Devices and post back what you find out. Once you've established the model of sound it should be easy to find the right drivers.