Suppose you have already installed codeblocks-12.11-setup.exe
And you don't want to deinstall it and reinstall with codeblocks-12.11mingw-setup.exe
You go to
http://tdm-gcc.tdragon.net/download to add the MinGW compiler (called GNU-GCC in CodeBlocks) yourself
You can do it and it will solve this problem, but when the MinGW Installation Manager opens:
be sure not just to install the C++ but also the C compiler!!
Then CodeBlocks is satisfied as it has all the files it needs in the C:\MinGW\bin
You can check if all the files it says it needs are there in CodeBlocks:
Settings -> Compiler -> Toolchain executables
Perhaps you also need to install the mingw32-base from the MinGW Installation Manager,
I don't know, I tried that 2nd myself, the C compiler seems essential.
Also in Settings -> Compiler -> Compiler settings
I checked -std=C++11 to be able to compile the new standard.