Right-click on the AVI file. Select Open With > Choose Program > Wordpad.
You'll see a load of 'garbage' but, near to the start, you'll find "vidsxxxx", where 'xxxx' is the codec used for the video (e.g. you might see 'vidsMP43' which tells you that you require the MP43 codec).
Then go to this site:
http://www.fourcc.org/
and click on 'Video Codecs'.
Look through the list to find the relevant codec and the appropriate website. Theoretically, that should take you to the original developer's website, where you can download the codec. Unfortunately, the information you provide suggests that the codec might be SunPlus's SP44. There doesn't seem to be any reliable stand-alone version of this codec available. However, ADS Technologies is a well-respected company and their website includes a download for a device driver which includes this codec:
http://www.adstech.com/products/USBInstantVide o/downloads/drivers/USBAV170.exe
(NB: That's an executable file. While the source is, as I've stated, well-respected, please virus-scan it before running the application).
Alternatively, switch to a media player which doesn't rely on obscure codecs. I'd be very surprised if these players didn't work:
http://www.videolan.org/vlc/
http://www.gomplayer.com/
Chris