How do I change video format from 320x240 to 496x368?

I have video files in both Quicktime and Windows Media Player Format. I want to upload this video to the internet, but the website has specific criteria of 496x368 in Quicktime format. What should I use to convert the video format from 320x240 to 496x368? And can you give me step-by-step directions.How do I change video format from 320x240 to 496x368?You can use a variety of programs but my favorite is Xilisoft.

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