Thanks a lot for your reply on my question. I'm going to work through your points and will give you some feedback after.
Ok, I'll try to explain what I have done.
The driver could be the cause, because I've installed it just one week ago. Therefore it's also the latest version. Maybe I should remove it completely?
Daemon was installed once. It is already removed and the uninstaller you recommended me says that there was no driver called sptd.
To your last point:
I'm working through the thread. Because I'm no native english speaker it will take a bit longer.
But again, thanks a lot for your help!