Edit file write protected by superuser rigths

[Armin Goralczyk]

Hi
How can I edit a file that is write protected by superuser rights? I  
can visit the file but it is read-only. I removed read-only  
protection by C-x C-q (toggle-read-only) but after editing I cannot  
save the file. Minibuffer says:
File fink.conf is write-protected; try to save anyway? (yes or no) ->  
yes
Doing chmod: operation not permitted

So how can I save the file provided that I can have superuser rights?

Thank you
Regards
Armin