I installed Returnil on my father's vista. When I right clicked to choose "Enable", the screen went black and stayed that way. This happened when I tried before a couple of months ago and so I just uninstalled it. But this time I manually turned the computer off and started it up again. I then decided to temporarily disable Zemana. I was able to enable it with no problem. I did also exit out of a couple other insignificant items in the system tray like Free Download manager and Gadwin print screen, but I am sure it was Zemana. I just thought I should mention this.