How to get the Executable name of a window

I try to get the name of executable name of all of my launched windows and my problem is that:

I use the method

UINT GetWindowModuleFileName(      
HWND hwnd,
LPTSTR lpszFileName,
UINT cchFileNameMax);

And I don't understand why it doesn't work.

Data which I have about a window are:
-HWND AND PROCESSID

The error is: e.g:

HWND: 00170628 
ProcessId: 2336        
WindowTitle: C:\test.cpp - Notepad++
GetWindowModuleFileName():  C:\test.exe

HWND: 00172138 
ProcessId: 2543        
WindowTitle: Firefox
GetWindowModuleFileName():  C:\test.exe

HWND: 00120358 
ProcessId: 2436        
WindowTitle: Mozilla Thunderbird
GetWindowModuleFileName():  C:\test.exe

Note: test.exe is the name of my executable file, but it is not the fullpath of Notepad++... and it make this for Mozilla Thunderbird too... I don't understand why

I use the function like this:

char filenameBuffer[4000];
if (GetWindowModuleFileName(hWnd, filenameBuffer, 4000) > 0)
{
    std::cout << "GetWindowModuleFileName(): " << filenameBuffer << std::endl;
}

Thank you for your response.