btw: The reason i thought 'Pelles C' has a Gui Designer is because of this:
http://www.smorgasbordet.com/pellesc/images/screen2.png
Wishful thinking.
...vm
That's the dialog editor... used for pop up dialogs like the "find" one in the screen shot.
You can make simple programs that are based upon a dialog if you only need one window but they are rather limited in their capabilities. If you are writing something more complex, then you need to create "top level" windows with the RegisterClass(), CreateWindow() and CreateWindowEx() api calls... as explained in the tutorial I linked for you.
Generally a windows program has it's main window which is created "top level" and a series of dialogs that pop up to aid in data entry, settings, searching, whatever.... The dialog designs are not part of the main program code, rather they are stored in the "resource" part of the program, are owned by the main window and are loaded and unloaded on demand
See the attached image for an example....
Edit:
Also note that as you get more into this you will find the *absence* of a formulaic GUI designer is an advantage, not a problem. For example: Most top level windows are resizeable and the support code for that can be rather complex in GUI designers, whereas when doing it yourself, you can streamline and customize your code exactly for your needs... This most often results in smaller programs that run considerably faster than what you'd get from a cookie cutter GUI designer.
Besides... creating your own main windows is not really all that hard to begin with. (See the forger's tutorial)