Transferring DSLR memory card to another?

From my friend's SD card, I transferred our school project's videos and photos to my own SD card, it was successfully copied but when I inserted my memory card back to my Canon DSLR and scanned the files, only the photos can be seen not the videos. Though when I connect the memory card to the computer I can see the videos saved in the SD card.

What can I do? I need to have a copy of the videos, I should be able to watch the videos in my camera.

P.S
If this helps, my friend owns a Nikon and I own a Canon, I transferred the files from her Nikon's memory card to my Canon's.

How old is your Canon? Does it have video capability? If so, is it as high resolution as the Nikon? If you are going from a 1080p Nikon to a 720p Canon you won't get it to work, but your computer will be able to play both.

Also do the Canon and Nikon both record in the same format? The Canon will only play back the same format and resolution that it can record in.

Your camera is NOT a media player, although many people seem to think they are. It is not made to play back videos from other sources, only the video it captures. There's nothing you can do to change that.

You think you should be able to play the video, but Canon thought otherwise.

If there's one thing that many people will tell you it's that you should never put your memory card like that into another camera, or different brand. Sure it may seem like no big deal, but it could create problems when it comes to viewing the media on it.