My employer has developed a paranoia about admin rights, and this could be true for many other large corporations. It would make life much simpler if there was an alternate install that did not require admin rights (possibly with some loss of features). Ideally, if it would cost nothing in features, a change to the standard install that removed the need for admin rights would require less support than maintaining two installs.
To get around the "protections" imposed by help desk I've begun installing whenever possible to a c:\bin directory. The various software that work without admin rights using this alternate for the Windows directory structure place all supporting files in a single tree under the program's install directory. This may be inefficient since some supporting files may be the same for multiple programs and save no space through reuse, but it is straightforward.