That's a very annoying issue in Windows, and it's caused by the codepage used by the console (it's different to the one used in the graphical environment).
I'm just checking Code::Blocks' available encodings and I see WINDOWS-1252 (Settings -> Editor: Default encoding when opening files) in its list.
Here you can see how to change the codepage of the console to 1252.
In short, you must be sure the codepage used by the console and the one you save your source files in match.