So i've played morrowind for some time now and it was ok. Then i changed my windows form millenium to 7. Since then morrowind has a problematic behavior. Some times it crashes when the music changes to battle music(but not always).Sometimes a message pops up claiming that some files are missing. Some times the dark brotherhood armor is white like the texture is missing. I am quite sure that this has to do with my new version of windows but i dont know how to solve the problem

It would help to know what the warnings say.

You will want to move Morrowind out of Program Files on the newer version of windows.
You can simply drag/drop your Bethesda folder into a new folder, like C: Games

That may fix your problems right there, but seeing your warnings will let us know the specifics and if it's related to mods or not.

Well i played for half an hour and it seemed that the advice you gave me worked since most of these problems did not occur again. However some seconds ago i was attacked and the game crashed probably because it couldnt load the correct music battle theme (it must be a specific theme since i havent got problems with other battle themes)