Anyone can help me with my comp?
 

When executed, it will display an ON/OFF Switch icon in the upper left corner of the desktop screen.
If the user clicks on the switch icon, the background of the desktop will turn black and all other icons except the switch will disappear.
And if the user clicks on it again, the screen will go back to normal

LOL that is what the virus does.

The problem was, he downloaded that program a time ago, nothing strange happend. And today nothing worked anynmore. But system is now clean,

Andre

Just see what is running on your pc and remove the exe program that is causing it.

look in your startup folder for a strange program.