Bought QuickTime MPEG2 component - "installed" but it's not there

Question

I just bought the MGEG2 component and ran the installer - it said it was going on my hard drive, ran the progress bars, etc., and even gave a nice cheery "installaiton Successful" announcement with an attractive green check mark,  Too bad it didn't do jack for QT's ability to open files.
When I look in my (hard drive)/Library/QuickTime/  directory, it's not there. 
It should have a resource filenamed "QuickTime MPEG2.component" (everything there is for audio (AC3), Div6, Perian, Flip4Mac and the Save as AVI component from MPEG Streamclip.)
Antbody understand why it's not where it should be?
Reference info:
OS 10.6.7
QT Pro 7.6.6
MacBookPro (Intel 2 GHz)
component installer v. 7.6
  (creation date Jan 14, 2009)  <- too old?

Answer 1

1) What part of their MP4 doesn't my version of QuickTime understand?  (It reads a lot of mpeg-4s, what does it need to know?)
You have two different facets here.
The first is MPEG-4/AVC (H.264) video multiplexed with AC3 audio wrapped in an M2TS, MPG, or MPEG file container. This has many problems. On the one hand the video is MPEG-4 and so the QT MPEG-2 Playback component cannot decode it but it is wrapped in an file container that is basically telling QT to use the QT MPEG-2 Playback component for video playback (i.e., much the same as why VLC considers the content MPEG-1/2 data because that is what both media players expect even though VLC can actually handle the audio and video data in this wrapper). On the other, QT is not natively compatible with AC3 audio and cannot play it natively even if it was able to "demux" the blocks of audio and video data properly and synchronize the two to a common external time reference which is the basis for QT media technology. (I.e., The wrapper being used is based on spatial synchronization of audio and video data interspersed in a single data stream rather than the temporal synchronization of up to 99 parallel data tracks normally used by QT—a basic difference in player technology akin to trying to play a BD disc in a CD player.) Normally, the way around this problem is to use iMovie '08, '09, or '11 to import your content. iMovie contains a special import/converter module to handle this content. Basically, it converts the AVCHD video to AIC (Apple Intermediate Codec), converts the AC3 audio to resampled linear PCM (AIFF) and applies timing offsets as may be needed to ensure synchronization between audio and video content. This data is then wrapped in the generic QT MOV file container making the files compatible with any/all QT based applications. Unfortunately, the special module cannot be used by files already imported to your hard drive at the "Finder" file level.
As to MP4 (SD MPEG-4, Chapter 2) content, these files may or may not be compatible with QT depending on how the audio is encoded, the file container actually used, and/or how your system is actually configured with QT components. In most cases, making the content compatible may be as easy as doing nothing, to changing the file extension or copying the data to a real MOV file container to using MPEG Streamclip to convert/handle the audio content.
2) Why does VLC show the file properties as MPEG-1/2?
Like QT, when VLC sees the wrapper file extension, it "assumes" the file contains a specific type (or range) of data types and reports accordingly. The main difference here, is that VLC can actually play the AVCHD data natively while QT cannot.
By the way the MPEG-2 description jived with a review - CNET, I think -  which I'd read online.  No doubt this will provoke another one of those explanations that always boil down to "you don't understand, the wrapper isn't telling you what's in the files"  responses.  Is there a tool for telling what the thing actually is?
Interpretations can sometimes be confusing. HDV content can also be described or reported as MPEG-1/2 content since it is sometimes described as DV100 encoded data wrapped in an MPEG-2 file container. As to what is actually in a file container and utilities to read them, there are a number of such available as free downloads. Unfortunately, many will have the same problem with MPEG/MPG containers if they bother to read them at all but do really well with other file containers. Since most of the content I deal with is MOV, MP4, and/or M4V, I tend to use the free VideSpec and/or Dumpster utilities. In my case I am more worried about MPEG-4 Profiles and Levels, entropy encoding modes, fourCC identifications, key frame frequency, key frame data rates, how the data is distributed between key frames, and the like when trouble shooting problems and most of my dealings with AVCHD are limited to the conversion of DVR/BD content to TV2 compatible content since I don't even own an AVCHD camcorder (and still prefer HDV for editing purposes).
The broader question remains - is QuickTime meant to be general purpose, at least as a player?
No, it isn't. As previously stated, QT technology is based on temporal synchronization of multiple parallel data tracks (up to 99) to a common reference clock and not spatial synchronization by interspersing of blocks of data within a single stream or the interleaving of data frames (which QT can handle because the data is only out of sync by one half-frame per n-1 tracks). This is great if you mask, layer, window, etc. content within a single player but severely limits QT compatibility with older and/or currently competing technologies. In short, pick your player/converter based on the technology used in the source file and not because you think QT should be an all purpose, one size fits all multimedia utility. If FLV Crunch meets your needs, then by all means use it.
I took some similar files I got from a recent model Canon to a video professional's (family) and they couldn't be read by a current version of FinalCut Pro.
Which model Canon? Which "current" version of FCP, the suite or the new FCP X release? Do you have a short snippet you can upload for examination? Have yet to research the pros and cons of the latest release but plan to do so next month if/when I have the time. (I.e., users seem to either really love it or really hate it.)
PC video straightforward, Mac a colossal hassle until you find the right 3rd party application: does that sound wrong to anybody else?
If you opt to use an import work flow that preserves the QT file incompatibilities instead of a work flow that ensures QT playback, conversion, and editing compatibilities, is it the fault of the software or the user?