The CJPG codec is used by Creative Labs Video Blaster Webcam Go control and you may need it to play back files captured using this hardware. The codec itself is not easy to find but Jeremy Bendlin sent the following information which should allow you to get hold of the necessary driver.
"I spent countless hours trying to get some Avi's that my relatives sent to run. Here is my solution:
Go to Creative's site and download the driver files (vwgplusdrv.exe - 807k) for the Video Blaster. Run the file. Copy "ctwbjpg.dll" to "c:\windows\system". Open your "system.ini" file and place VIDC.CJPG=ctwbjpg.dll following [drivers32]. It should look like this:
Reboot the system and cross your fingers. I cannot guarantee this will work on all systems, this is how I got it to work on mine. I tried getting help from Creative, and they said download their software, then try to view the files. Their program would not run on my system without the webcam. So don't waste your time with the 8MB control program, as I have already done that myself.