how can I stop httrack adding this sort of comment to each 
file

<!-- Mirrored from www.xxxxxx.com by HTTrack Website 
Copier/3.x [XR&CO'2004], Thu, 13 Jan 2005 15:46:13 GMT -->

I am hoping to use httrack to compare the difference 
between a site before and after changes, but becaus eof 
this comment all files are always different as it includes 
the time it made the mirror!

thanks in advance