Based on the subject of your question "Quicktime Components Intel Mac," I'm assuming you want to stay with Quicktime as your player.
The first thing to do is to download and install a few codecs that will help free your QT player to handle those pesky AVI's.
1) Download the DivX component for your Quicktime Player here:
http://labs.divx.com/LatestMacCodec
Once correctly installed, try your movies again in Quicktime.
2) If you are still having issues, you can also download and install the XviD component here:
http://n.ethz.ch/student/naegelic/download/
3) If you run into movies that won't work in your Quicktime Player after all of the above, I would also suggest downloading the Flip4Mac component, although this component is primarily for WMV files, and also, to get the latest Flip4Mac component to install properly on you intel machine, you need to run your installer under rosetta.
Lastly, I have had great success with the VLC player build for intel mac as an alternative to those files Quicktime can't handle. You can download that player's latest release here:
http://nightlies.videolan.org/build/macosx-intel/