How can I name short videos I take on my digital camera?

Once I download them and they show up on my computer i have to watch all of them all over again to find the one I am looking for. I use irfanview and I know there is a way to resave them or something but I am not familiar with how.

if you are using windows - open file explorer and go to the folder that contains the videos. right-click on the file that you want to rename - and select the rename option...just be careful that you do not change the file extension (for example - .mov .mpg etc...)