Decoding AVI files using Encore CS3 On Macintosh

I have some AVI files that I want to import as Assets into Encore CS3.

I AM USING A MAC!!!

Information about my files (Retrieved from the advanced information tab of the
information window in VLC for Mac) in shown below.
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Stream 0
     Codec: XVID
     Language:
     Type: Video
     Resolution: 640 X 480
     Frame Rate: 25.000000

Stream 1
     Codec: a52
     Language:
     Type: Audio
     Channels: 2
     Sample rate: 48000 Hz
     Bitrate: 256 kb/s

General
    Duration: 0:24:15 (Obviously this varies from one file to the next)

Meta-Information
     Setting: HAS_INDEX IS_INTERLEAVED
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I should think the information provided above is all that is necessary to solve
my problem. However, if you need statistical information (provided in the
statistics tab of the information window) please tell me.

When I import the AVI files (AS Assets) I receive an error message saying;

'The Software that's used to decode the media is not available on this system.
Installing the correct decoders for the files you are working with may help to
correct the problem.'

I am pretty sure (Thanks to Bill Hunt) that what I need is a codec for decoding
XVID video files.
Am I right?
Is there such a thing for Mac?
Where Can I get it?

P.S: I don't want to convert my AVI files to .mov files or other compatible
formats because I have allot of files and not allot of time.

Ok! So DV AVI type 2 is a different video format to the one I'm using right?
Meaning I would need to convert my files using a video converter
But I would rather not have to convert them, It Takes Ages!!

In the day that's passed since you've posted, you probably could have converted
all your media, but anyway...

If you're for some reason you are still averse to doing that, I would
reluctantly suggest installing the Xvid codec on you Mac. Reluctantly, because
Xvid can cause havoc on some Windows systems, and I don't know how well it plays
on the Mac.