Why are my videos so small (frame size)?

I'm new to youtube video making and i record with a nikon l120 and the video records hd 720p. But every time i put the files in my computer and i convert the mov file to wmv. It like shows the two black lines, top and bottom like a widescreen video but when i post it on youtube its small.

if you don't understand what i'm talking about, please look at any video on my channel: www.youtube.com/user/AzNxLee

YouTube often creates multiple versions of the file, for different resolutions (your frame size). There's an option to change the resolution you're downloading (bump it up to 720) then make the video display full screen, or with some videos, increase the resolution actually being used. That's stuff for the person watching the video to do though, not something you set up for the viewer.

Uploaded video have two black lines on the video, I know this is video resize problem, usually because your video is wrong profile for youtube, so you need to convert your videos to right profile then upload onto youtube again to fix this problem, you could follow me to use Youtube Movie Maker to help you, it can directly crop the black border on the video sides, and it can auto convert any videos to right profile and format/codec videos then upload onto youtube, then can play well on Youtube without black lines, just Run youtube movie maker, select "Upload Video", then add your video into the file list, then press Crop button to crop the black lines on the video sides, at last press "Convert&Upload" button, the software will auto convert your video to right profile, then upload onto youtube with fullscreen, and the uploaded video will be played well on youtube without black lines, you can download it from makeyoutubevideo.com, and view below channel for some online guides, youtube.com/easymakevideo, hope it can help you.