> In your web browser, save an image to your HDD. Now
> try to save the image again. You will get an error
> message telling you the file exists, and it will ask
> if you want to cancel your action or overwrite the
> existing file (and sometimes you get the option to
> rename it).

But that is not what httrack does. 

It downloads only ONE copy of each file, no matter how many times it appears
in the mirror. (Think site icon or css files) It then modifies each html, js,
or css file to point to the where it put the file. 

Now supposed two different pages have two different image.jpg The browser
would overwrite the file and one page would display differently, where as
httrack would rename one file and adjust the reference.