Ok, I'll think of eru next time. I reinstalled Avast and got it to work. In the chest there were three dll-files: wsock32, winsock and kernel32. All have been replaced from cabs without any changes. The log didn't seem to be there though, so I'm not sure what other files got deleted.
I think I'll give up now and just accept that there is nothing I can do about my corrupt registry. In the present state, I can do everything I want, it just takes a bit more time and it's a bit more annoying. I'll fix windows next time I get home, where I have my cd.
Thanks again for all replies,
Dag