> some having broken jpg link. When i update it with httrack,
> some of my previously downloaded jpg will become a 1kb size 
> jpg files.. can this be prevented? I've enabled 'do not 
> purge old files'  and disabled 'do not redownload locally 
> erased file'

'Do not purge old files' will tell HTTrack not to delete files which it
downloaded previously, but are not needed after an update.  If the images have
been replaced and still used, then the ones you have downloaded will be
overwritten.

The 1KB size is odd though.  Are they actually images?  Are they maybe HTML
error pages?  It could be that the server is returning the wrong MIME type.

Providing an example URL might help track the problem down better.