hello i download qt sdk and started the qt creator and tried to do a simple empty project but it says The program has unexpectedly finished on the error list and i tried many examples but same thing happens , im using windows 7 x64 homepremium and mingw as a compiler what is wrong ??????

There could be issues with using Qt with MinGW on a 64bit platform. Have you followed this instructional wiki? The basic MinGW distribution doesn't truly work in 64bit, you need the w64 distribution of it.