Quicktime support for MPEG-2 missing from my Lion OSX. How to fix?

My OSX is Lion, (10.7.4) but the Quicktime support for MPEG-2 format is missing. When I look in the Quicktime system library there is QuicktimeMPEG.component & QuicktimeMPEG4.component, but no QuicktimeMPEG2.component. So, I presume its not there. How do I fix this? Do I have to re-install something? I had Quicktime 10.1 on my system, but have now also installed Quicktime 7.6.6.

I need to work with some MPEG-2 videos & convert them to MPEG-4 format. I gather I can do this with MPEG Streamclip, but not if MPEG-2 support is missing!