image upload error, iis 7.5, drupal 6

problem: using drupal 6, iis 7.5 on windows

enabled image module, however, there is a file upload error displaying extension not supported.

solved by

Changing line 117 in include/menu.inc:
if (!is_file($file)) {
to:
if (!is_file($file) && !is_uploaded_file($file)) {

source