Well I haven't really worked with Qt Creator and specially not with qmake (which turns those *.pro files into usable make files), so I'm not sure what goes wrong, but I'd still bet you have a miss match of libraries.
If you follow the Code::Blocks tutorial 1:1 it's guaranteed to work. It's just a matter of copying all the details...
Optionally you can also build your application on your own without any IDE. If the path to the MinGW binaries is added to the PATH environment variable you can just open a command line.
g++ -Ipath\to\SFML\include -Lpath\to\SFML\lib File1.cpp File2.cpp -o Output.exe -lsfml-graphics -lsfml-window -lsfml-system -lsfml-main