Can't open avi files, to quicktime, vlc, divX player... help!

I need help on how to open several avi. movie files I have downloaded onto my Mac (version 10.5). First, I tried to open them just simply on Quicktime player, but a got a 'this is not a movie file' error message, so I Google'd and found advice telling me to download VLC in order to open avi files to Quicktime player. So, I downloaded VLC and tried to open one of the files with that - except when it opened on VLC there was no video and only the audio sped up really fast (you know, where they sound like chipmunks xD) and then it stopped. So, baffled, I then tried to open it again on Quicktime, but got that error message again *

So I Google'd a bit more, and found advice telling me to download DivX Player, which should open/play avi files - so, I d/w'd it.... but alas, the files wouldn't play audio or video, it didn't seem to show up.

I've looked on the info when it's opened on VLC, and it describes the streams (not sure what these are) as having both mpga and mpgv codecs.... so do I need to download a program that can open these files? Is there a codec program I need still?

* OR, am I not using VLC player correctly?

Any help is appreciated, with clear instructions, because if you can't tell already, I'm really pretty inept with this sort of thing!!

Thanks.

 

So... mpga + mpgv files = IV50? Or are you just saying I'll have the same problem with my files as that person did with theirs? I don't think I have the same file-type, see. But maybe I'm wrong

 

It says the codecs are mpga and mpgv, is that not actually the codecs either? Wow this is confusing xD

I already have Perian installed