XnView Software

Yeap. Try asking them for a discount. I heared some people got this, by reffering to forum discussions or providing suggestions.

BTW, they changed name to duplicatevideosearch.com and released a new version recently. I've already upgraded.

There is a simple way (paid though) - http://visualsearchpony.com

This is a specialized duplicate video finder program, that automatically detects all video duplicates, including both exact and converted copies (various formats, resolutions, bitrates, etc.).