Codecs

I'm not certain about this but... there was a time when i had a codec pack installed in my PC, that when i used CCleaner to clean, some file associations begun to fail, the icons of those files associated with Media Player Classic, for example, didn't have the icons of MPC, no matter how much i set the associations. So i installed everything again, the codec pack i mean, but without installing the CCleaner, and so far, everything's normal...

Does the CCleaner somehow interfere with the association of the files with their programs?

Depends, did you just run the cleaner or did you run the registry "fixer"