When re-installing fails I think it's a problem with the ASPNET user. Before you reinstall the framework unregister the framework from the IIS (aspnet_regiis.exe -u). 
Usually after reinstallation everything should work again. 
 

This would be the configuration tag in the beginning in the web.config:
<configuration xmlns="http://schemas.microsoft.com/.NetConfiguration/v2.0">
When you insert this line will be automatically corrected to
<configuration>
when you start your DNN.

When you insert this tag in a .config file it will not cause to a complety stop of the asp framework. If checked this with parallel solutions and found any interference (why should it ???).

Thanks to all again. I could install dnn finally.

But there remains a small glitch that I didn't find out how to bring in IIS and MS SQL Server.

1. I used Install package
2. I haev chosen auto install mode
3. I built a page and closed it down
4. I don't know whether it can run again without IIS being connected
5. How can I restart the server and dnn everyday; I don't find it in start>>programs

I browsed Salaro's suggestions at http://www.iislogs.com/articles/dnnonw2k3dc/default.aspx but as earlier, they went bouncers.

Thanks in advance.

Raj