I am using qt creator , and i have a binary file (.exe) along with some dll files generated by Microsoft Visual C++ 2005 SP1 .
Now i want to use the functionality of binary file (.exe) in QT creator , please let me know how can i proceed ?
You can extend QtCreators functionality by creating plugins for it.
Google it.

On the other hand, maybe you mean you want to link your application to an external lib.
For this read the QtCreator documentation.