In windows movie maker, click on the Project tab at the top and select 16:9 aspect ratio. You had it in 4:3 hence why it's not in HD. Also, don't upload directly to youtube, instead render to your computer, then go to youtube and upload it directly from your computer. If your internet will allow it, render it in the best possible resolution and not the "suggested" resolution. This will be much better but as stated, only if your interwebz can handle it. Otherwise you will be uploading for hours for a 2 minute 1080P video. Let me know if it helps.