I've a serious problem with my Windows 8.1 installation. It won't even allow me to enter the login screen (everything is black).

I've installed Aero Glass for Windows 8 (glass8.eu) which adds a service called "Unsigned Themes". The problem occured when I edited services.msc, changed "Unsigned Themes" from automatic to manual and then rebooted.

Obviously it was a mistake. Windows won't even load the chrome user interface.

But if I can find a way to revert the service to automatic, everything will be fine. I don't want to reinstall my whole computer just to fix this thing. That would be a whole lot of work!

I have experience in fixing similar things in Linux environments, but this is Windows and I need help.

What I suppose I should do is the following:

1) Reboot into the console in recovery mode
2) Mount D:\ so that I may run the following commands as if I had booted into my Windows partition
3) Find the short name of the service "Unsigned Themes" (like for instance, "tlntsvr")
4) Run 'sc config <THE SHORT SERVICE NAME GOES HERE> start= auto'

Then reboot, and it should work! But how do you do this? How do you mount the drive and search for the short service name (I don't know the commands nor how to use them)?

I might add that I don't have any system restore images or the likes (I was about to create one as I was going to install Windows 10). I've tried booting into safe mode. Perhaps there's another way?

(I now recall that I also set the service "User Experience Session Management Service" as manual. That might be the source of the error as well.)

Is there a power user to help me?

Thanks a lot!