The following forum message was posted by fabioz at http://sourceforge.net/projects/pydev/forums/forum/293649/topic/4049708:
Hi there, not really sure...
Maybe they're trying to install it on a place where they don't have rights (such
as the program files), so, ask them to install on their user folder (although
this shouldn't be a problem if they're running as administrators -- but otherwise,
I'd advise to install on their user folder).
Or maybe the windows UAC (user access control) is making this happen, so, you
could try disabling it (see
-build-7000.htm for how to disable it).
Or maybe it got corrupted in the download? Have you checked if the
org.python.pydevXXX folders have been created in the plugins folder?