My xml function does not works in some operating systems

I have created a program to create an xml at the installed folder when the application starts.
It works in windows xp without failure. When i try it in windows 7 ultimate it does not works. But it works in all other versions of windows7
what is the reason?

The answer hasn't changed since the first time you asked.

In general, you cannot write to the installation folder of a program (under "Program Files") on any flavour of Windows 7 without first butchering the permissions. You certainly should not rely on that working unless your application runs with Admin rights.

If your application does not carry a manifest then directory virtualization will be used to give the program the appearance of working: the created files will go into another (per-user) location and only virtually exist in the restricted location. Other users will not see the virtualized files. See Scenario 2 here. For much more on this try here.

QDesktopServices can help find suitable locations to store information. On Windows you can use the SHGetKnownFolderPath function to find locations not available through QDesktopServices.