I thought I would give the WDM Driver a go again with MC20.0.108, and test the installation process.
I run my HTPC with a limited user account on Windows 7 Ultimate SP1, and anytime an installation needs elevated rights, UAC asks for the password for my Admin account. So the installation went like this.
1. Installed MC20.0.108
2. Activated the WDM Driver in Options -> General -> Features -> WDM Driver
3. The UAC prompt popped up and asked for my Admin password, twice in a row. (That seems to be something new. Perhaps once for an update to MC, and once to install the driver.)
4. A small dialogue window popped up and asked if I wanted to install the driver. I clicked the Okay/Install button.
5. A small MC message window popped up to inform me that I needed to restart the program to activate Feature changes. OK to close the message.
6. I closed and restarted MC, but not the Media Network services.
Then I set the WDM Driver as my default audio device. I didn't set up Zones. I am using WASAPI Exclusive mode as output from MC.
Movie Trailers in YouTube played through MC successfully, as shown using the Audio Path, and the room correction I have set up in MC made them sound much better.
So I was able to install and use the WDM Driver successfully. At least in this instance. It is yet to be seen if the same thing happens when I upgrade MC to the next version. It seems there is still some unexplained difference between the process on different PCs.
If you're a limiter user, to get past UAC you have to run as a different user. This means when it installs the driver, it can't write to your HKCU Registry hive. It writes the setting change to the admin user's HKCU Hive, not yours. So the next time you install, it removes the Driver because the setting itself never gets checked.
I don't believe that is correct. As far as I'm aware, when an installation program being run by a limited account requires and asks for elevated privileges, it still saves all settings in the limited user account's settings. I had to check that out for something else I was working on some time ago, and found a Microsoft article that explained this. I think that is what you were saying Hendrik, but missed a word;
"
When the Installer on the other hand runs elevated itself, so the entire process, both the installer and the helper which installs the driver, run as the other
[elevated] user."
If that caused the problem I would uninstall as the elevated user and reinstall as the limited user to fix the issue.