BleepingComputer.com: THM and MVI Problems

Ok so I am having some issues with trying to view video clips from my SD card I took out of my CANON POWERSHOT A470

Some of the video clips are in MVI format while others are in THM format (which I already know is a thumbnail)

I cannot view the clips in THM format which I'm sure is because they are thumbnails.

My question is why would some of my clips be unreadable and in THM format but others readable and in MVI format!!??

How can I change it!!?? And please don't waste time explaining what the files are as I already know I just can`t figure out how to change it so I can view all of the clips! It doesn't make sense why some of the clips are in THM format and others not!! I need too make a video out of the clips but I can't if some of the files are thumbnails!

How do I make them in a readable format?

Thanks in advance!!