Windows deployment is a huge pain that isn't documented well and is full of gotchas. This is roughly the process you have to go through:

1. Compile your app. It won't run when you double click the exe because it is missing loads of DLLs and QML files.

2. Open a command line in the exe directory. Run the following command, giving it the path to your source directory and the exe path.

C:\Qt\5.4\mingw491_32\bin\windeployqt --dir out --compiler-runtime --release --qmldir ../../path/to/MyProject MyProject.exe

3. Copy the exe into the output directory.

copy MyProject.exe out

4. Observe that --compiler-runtime is totally broken so copy the runtime manually.

copy C:\Qt\5.4\mingw491_32\bin\libgcc_s_dw2-1.dll out
copy C:\Qt\5.4\mingw491_32\bin\libstdc++-6.dll out
copy C:\Qt\5.4\mingw491_32\bin\libwinpthread-1.dll out

5. Rename C:\Qt to C:\Qt2 so we can be sure when we run the program to test it it isn't picking up any system DLLs (the path to c:\Qt is encoded in the EXE).

6. Run it, it should work.

7. Upgrade your system install of Qt.

8. Run the program again. It fails. WTF?! Well remember I said the path to c:\Qt is encoded in the exe? Apparently the system Qt install has a higher priority than looking in the local directory and if it is incompatible the app won't load it.

9. The solution is to create a file called qt.conf with these contents:

[Paths]
Plugins=.

10. Add it to your system with the alias "/qt/etc/qt.conf"

11. Repeat all the above steps. It will now hopefully work even if there is an incompatible version of Qt in c:\Qt

12. Try and run your program from Qt Creator. It doesn't work!! Because of the Plugins=. path it now no longer finds the Qt version in c:\Qt and won't run. ARGHGH!

This is way too complicated, buggy and undocumented IMO.