As an option, look at these assemblies, where compilers build them are located there. As far as I remember QtCreator is present in their composition.
Added a bit later:
I downloaded the x64-Qt-4.8.5 + qtcreator-2.8.0-RC- (gcc-4.8.1-seh-rev1) .7z build, unpacked it. In the PATH variable I registered the path Qt64-4.8.5 \ bin and ported64 \ bin. Next, in the Qt64-4.8.5 \ bin directory, create a qt.conf file with the following content:
[Paths] Prefix = D:/programs/prog_dev/cpp/Qt64-4.8.5
D: / programs / prog_dev / cpp - the directory where I unpacked the downloaded archive.
Now you can run QtCreator, Assistant, etc. projects are created and compiled, help is read.