My sound at playback was so low, I had it at full volume but barely could hear it. I think it happened after i install a usb software for a “Real 5.1 game sound card”. I uninstalled and then also did a repair on 4.0. did a repair on 4.0 did not resolve. I rebooted computer, did not resolve. I removed 4.0 from my computer and installed 3.78 and it worked. Then i updated to 3.79 and its still working. I then unistalled 3.79 and installed 4.0 and now it works again with 4.0. Hope this helps
