don't install on top of another.
Best strategy :
1) Manual install MingW (see Wiki) : basically unzipping and run the GDB installer
2) add the bin path of that MingW to your path (eg C:\MingW\bin)
3) download wx unicode dll and CB nightly, unzip (7 zip) both in a directory
4) codeblocks.exe ---> double click it ;-)