You have a lot of options and you could use a lot of tools as described by Charlie Martin. I think that if you want the easiest path, you should use wxDev-C++ which is Dev-C++ bundled with the wxWidgets GUI library. After you install it, you can directly develop GUI applications without need for extra configuration. Maybe Dev-c++ is an old IDE, but you already use it and you know it. And wxWidgets is a solid GUI library.
