Thanks Julien,
I create a new web sits called Compuseum2. I stopped the DefaultWebSite and I started the new one.
I also moved the directory, containing the files of the dnn installation package to a new directory, which is C:\WebSites\Compuseum 2. I just put the directory into my dovuments folder first, maybe thats a problem.
Result: The same as before, error 500.19 ... nothing helps.
So, I have a dedicated web site in my ISS tree view, running, pointing to a folder c:\WebSites\Compuseum 2, both folders have all rights granted to IIS AppPool\Compuseum2, and also the sub folders share that rights, I checked it out on two samples.
I try to access the web site with IE using http://localhost/Compuseum2 on the same machine.
Trying http://Compuseum2 I get error 404, so I am shure I access the site, but rights were not set correctly for what reason ever ...
This procedure is different from that described in the documentation, results were the same.
Maybe some step foreward. I try something in the IIS management console like 'Handlerzuordungen', but this time I get a message, that the section at line 83 of the web.config file isn't applicable ...
So its seems, I don't have an accees rights problem any longer, but it still fails some steps later ...
With best regards
Gerhard