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I too lost my CD. Here is how to get latest Version 5.7 installed on your computer.

Go to the Canon website, go to the downloads for consumer products, 
select your camera (or any other camera if Zoom Browser V5.7 doesn't show up.) 
Download file ZB570UPD_EN.exe. Use Winzip to unzip that file to a temporary directory. 
In the folder, browse to INSTALL\Common and run file Install.exe.

This will bypass the check of whether the old version is installed or not 
(and its completely unnecessary, believe me.)

It is, by the way, ten times better than the old V2.x! Good luck to all!