"When i put the disc in the laptop, i keep getting a message saying the file format is not supported"
Is this the operating system giving this message or is it the application that is trying to play the video. ?
could be a codec problem
without all the details, a couple of quick and free ways to try and get round this is to download VLC media player
http://www.videolan.org/vlc/
it will play just about any type of video file thrown at it also download and install the K-lite codec pack
http://www.codecguide.com/download_kl.htm.
Possibly the DVD-RW could be corrupted
If its a Canon proprietary video format then if K-lite cant handle it Canon hopefully should produce a codec that you can use.
If this Canon records direct to disk can the Canon play back the file via its own screen.
Or was the film tranferred to a PC and written to disk that way, if so do you still have the original footage ?