Thank you for your prompt answer.
There are two things wrong. The first one was my confusing about different Eclipse installations and workspaces. This was my problem and I have fixed it.
After fixing, I see the plugins and no errors in the Error Log View. I can create a Hibernate configuration, fine. But the XML editor was not available neither with a simple double click on a hbm.xml file nor in the file association dialog.
The solution for this problem was to install it by the Eclipse -> Help -> Software Updates:
http://download.jboss.org/jbosside/updates/development/
After installing the Hibernate Plugin in this way it works fine.
I do not know the difference between extracting the ZIP into myECLIPSE_HOME and installing by the internet, but now it works.
Again thank you for help and sorry for my confusing.