I thing the problem that because i'm using common control dialog and this is not work in vista, do you have solution for change common control with another ocx and not problem if running in vista.
If you do not want to bother about copying and registering the comdlg32.ocx file (for which you might need administrator rights anyway), tell the developer of the software to check out following project, that shows how you can use the common dialog box (open and save) without using the ocx file and thus without need of registering it. It uses the comdlg32.dll directly with APIs, which is installed already on windows! http://www.ws-software.co.cc/TComdlgAPIEng.html