Now this is a quite good example of codec packs' weaknesses.
You install the codec pack, it configures MPC and associates with browser, DirectShow.... etc., then install QTA or RA and at that point, your computer is already messed up.
If you really(!) need codec packs, can choose
K-Lite Mega Codec Pack which includes QTA and RA in1.
Alternatively, you can choose to install a K-Lite Pack, and the LITE version of
RA, which includes the codecs only, not MPC. QTA can be also installed without MPC, just deselect it during installation.