A firewall won’t block all viruses, you really do need some anti-virus program running.
Download either
AntiVir or
AVG Anti Virus and update and run one of them. They’re both freebies.
Also, go to
Gigabyte UK and download the latest audio drivers for your board (enter your board number at the top of this page). Whilst you’re at it, download and later install any other drivers from that list that are relevant.
Lastly, completely uninstall all the old sound drivers, including any folders in Program Files on C drive. If you want to use
This Program, Reg Edit, you can easily remove any registry entries relating to the sound drivers. Word of warning: Be VERY CAREFUL when using Reg Edit, if you’re not sure what something is, LEAVE IT ALONE. Reg Edit is free software, btw.
Only remove registry entries that you can positively identify as sound software entries.
After all that, install new drivers that you’ve downloaded from Gigabyte UK and let us know how you get on.