[face=Arial][/face]Last week I checked the software installed on my computer. And I discovered the following entries:
Microsoft.NET Framework 1.1
Microsoft.NET Framework 2.0
Microsoft.NET Framework 2.0 Language Pack - Deu
Microsoft.NET Framework 3.0
Microsoft.NET Framework 3.0 German Language Pack
Obviously these software packages entered my computer by automatic updates. Now my question: Are all these packages indispensable? And what for? The websites of Microsoft I found not very helpful. Perhaps Framework 3.0 is the newest version of Framework? The Space needed for all these software packages amounts to 450 MB.  

They are Microsoft's latest thing for developers.
You really only need them if one of the applications you are using requires them.
ATI's control center for its newer video cards requires .NET to install and run it. Other companies are also putting out applications that use .NET.
The latest framework is 3.0.
Home page for .NET
http://www.microsoft.com/net/

Thanks to dlwolff0 for answering. In the meantime I have tried to deinstall all frameworks using windows install clean up thus following the advice of Microsoft support. The result has proved as catastrophic. After that I had to reinstall framework 2.0 and framework 3.0 in order to be able to deinstall them by add/remove software.  Now I am left with a nonexisting framework 1.1, this software however still on my computer without any possibility to detect it. I got this impression because updating my computer I always get the notice that I should download and install the service pack 1 for framework 1.1. When I try to install the download version of framework 1.1 I am getting always an installation error. That's just great.

Sounds like some registry entries for ,NET framework 1.1 were not removed when you uninstalled it.
You could try using Ray's RegVac program to remove them or use regedit and search for and remove them manually if you are familiar with using it.

To dlwolff0,
thanks again. I have alredy tried regvac und also deleted some entries in the registry, but without success. After a second complaining to Microsoft I got another mail which I tried but unsuccessfully. A third complain resulted in a new mail and - wow - that was successfull. But now I have framework 1.1, 2.0 and 3.0. According to my information 2.0 and 3.0 are connected and sufficient. Now I have asked Microsoft if I could deinstall Version 1.1

In order to close this subject:
I got the answer from Microsoft, that there are some older programs which still need framework 1.1. So it should be better to keep it.