I updated the AMD graphics driver and it quietly updated the HDMI audio driver. The HDMI audio continues to work fine, but normal audio on the netbook has gone. I tried uninstalling and reinstalling the conexant audio driver, but on reinstalling it said "error no device found" and refused to install.
So now I can only hear anything if I connect the netbook to the TV.
I've tried intalling IN2AUD32WW5.exe and IN2AUD44WW5.exe but they just refuse to be installed.
Using Windows Restore to re-install the conexant driver will help you to solve the issue.