my computer wont let me save a picture?

Ill try to save a picture on my desktop and it will say: you dont have permission to save here, contact the administrator. and i am the administartor, at the moment i am using a internet connection at another persons house though, maybe thats affecting it? and it will said do you want to save it in "myname" and i say yes then it says do you wants to save it in "my pictures" then i press save and the error message pops up again, and it wont let me save anything. HELP ME D: