If you build it (Qt and application) on Windows 7 and want to run on previous version of windows then you might have problem like you have :] I have a Windows 7 x64 and Qt built from sources with VS2005 and I'm unable to run my app on windows XP even with all the dependencies verified with Dependency Walker (and it is depends.exe with "s" at the end :P). The solution is to rebuild your app on Windows XP in this case.