Sorry, I forgot to tell that those files I mentioned were already in the Virus Chest of avast!
Anyway, I did disable SVI and scheduled a boot time scan. This time, avast! found again several viruses on my second hard drive which I don’t use at all (the only reason I didn’t put it into the wastebin so far is that I didn’t find the time), and one on my main hard drive.
One is called Win32:Adware-gen, the other three are called Win32:Spyware-gen.
Does this mean, my computer is not infected by them yet but would have been infected if I had started those files in some way?
Or is everything lost now?

However, I downloaded and performed those programs Freewheelin Frank told me, but there are new versions on the internet so that I updated them and will perform them again now.

So far, the anti-rootkit programs told me there were no rootkits no my computer; the spyware-programs gave me several alerts, most of them TrackingCookies, but one Trojan and some Adware was found as well.
After having performed the not-updated versions, I ran HijackThis again just for checking this spyware “PromulGate”-thing, and it was not running anymore.

I will run the programs again and afterwards tell you what’s going on here. If you come to the conclusion that it would be better deleting and formatting everything and starting anew, tell me soon so that I can prepare myself… :frowning: