As it has been mentioned, Windows-based servers have trouble with the path to move the uploaded file to when using move_uploaded_file()... this may also be the reason copy() works and not move_uploaded_file(), but of course move_uploaded_file() is a much better method to use. The solution in the aforementioned note said you must use "\\" in the path, but I found "/" works as well. So to get a working path, I used something to the effect of:
...which worked like a charm.
I am using PHP 4.3.0 on a win2k server.
Hope this helps!