I have +/- the same problem on a friend's desktop.
Yesterday i installed 7 7068 64bit on his M2V mobo running Realtek HD drivers
First, many drivers weren't accepted, so i had to force the install. I dwnld the R2.21 version, installed it flawlessly. So had sound. But today, no sound anymore! So i went to Windows update, but there was no new driver
. I uninstalled-installed 4 times, with no more results. This is so annoying now i want to throw his PC through the windows.
Mind each time i uninstall-install, i do it after a reboot.
Any idea about Realtek audio HD?