converting videos for imovie

I tried searching this forum but couldn't really find the answer... of course the problem is I don't really have a great computer tekkie vocab at my disposal and hence can't find the correct words to search with to get answers.

OKay... I opened imovie and tried to import video clips to practise on. But the extensions, .mpeg .wmv and .mpg won't open as I guess they are not supported. How can I convert them? I tried Handbrake (new ver.) but after selecting the right boxes (output mp4 and video code mpeg-4 FFmpeg) and pressed start.... nothing got converted after it said that it did. Hmmmm. Maybe I checked the wrong boxes??

Does anybody know?

Thanks

Try downloading and installing Perian and Flip4Mac, Perian extends a host of movie codecs for QuickTime, while Flip4Mac adds support for Windows media.

Perian - The swiss-army knife of QuickTime® components

Windows Media® Components for QuickTime