Yay, finally a topic on these forums that I'm qualified to reply to! LOL
The best thing to do to fix the problem is to work backwards.
Start by uninstalling the Norton software. Once it's uninstalled, reboot the computer and pick a restore point from PRIOR to the date that you installed Norton. Restore back to that date, then reboot again.
Does the sound card work once you do that?
If not, then on to the next step.
Go to the Device manager to see what sound card is installed on your pc. Alternately, you can check the software disks that came with the pc for the brand.
Once you have the name, go to their website and do a search for software driver updates. For instance, if you use a realtek soundcard, head to realtek's site....and so on.
Download the drivers and any other software updates they offer, then install them, following the instructions carefully.
Reboot your pc again and check to see if that corrects the issue.
If you still don't have sound, post again and we'll head to the next step, ok?
SB