copying texture onto identical object I have modeled a house and have already placed windows in different parts of the house. Each window consists of several objects. These windows (consisting of several objects) are identical and are only moved in their position. Now I want to texture only one window and all windows should get that texture. So if I change something on my "main"- or "master"- window/object all windows should get that change in texture as well. I don't want to have to texture each one individually. 

Did I had to do something before copying or is it still possible? What I don't want is to texture it first and then copy it.

Feel free to contact me if you have any questions. Thank you in advance for the answers!
If all your windows are identical you can link their UV maps and materials. Better yet, you can link all the object data if you want them to be perfect clones of one another.

You can do this by selecting all your windows (make sure the last one selected/highlighted in yellow is the one with the proper material data) then press CtrlL and selecting Object Data, Materials, and/or Transfer UV Maps.