The trick with using online converters for videos is to find one that works when you need it. A converter is needed to change a video to a type of file needed to add it to itunes, PowerPoint, or even to play from your flashdrive. Here are some to try:
: This one is easy to use, but you send the video to be converted and receive it back in an email. This can take 2 hours or a day, so plan ahead if you want to use it.
Hope this is helpful. I know finding a reliable converter can be tough, but these are a good place to start.