> I use ZTree to incrementally backup weekly from one hard drive to another
> (remote) hard drive. I do this by Alt-Copy of all files in the specified
> directories that have the Archive attribute set (tagged by visual inspection
> when the files are sorted in date order). And after each Alt-Copy, of course, I
> remove the A attribute from all copied files.

To tag all files that have the archive attribut set you could just do "[Alt+T]ag,[A]ttributes,[+A],return".

> Apart from the tagging being a bit tedious, this approach means that there is an
> increasing number of files on the remote drive that have been deleted from my
> drive. Is there a simple way to do a true incremental backup using the Compare
> functions in Ztree? There are about 6,000 files totalling 2Gb altogether.

This is a bit more tedious and I think to make it convenient you need to write a macro. The first thing that has to be done is the copy of all new or unique files from the source to the destination. In a second step you have to delete all unique files from the destination.

The actions step by step:

*) First step: Copy files.
1.) Make sure you have file spec set as you need it (usually *.*).
2.) To tag the files that should be copied move to the source dir in dir window and log the whole drive with *.
3.) Invoke [Alt+C]ompare.
4.) Specify the destination dir either by typing or pointing to it with F2. Once you have done it this path is stored in history and you can assign a letter to this path so that a macro can retrieve it from history directly for future use.
5.) Choose to tag files that are [U]nique and [N]ewer (which is the default), or, what I would prefer because it is more safe: Use [I]dentical and Ctrl+[I]nvert,[T]ags after step 6.).
6.) [B]ranch into file list.
7.) [Alt+C]opy to destination, choose [R]elative paths and confirm overwriting existing files.

*) Second step: Delete unique files at destination.
1.) Make sure you have file spec set as you need it (usually *.*).
2.) To tag the files that should be deleted move to the destination dir in dir window and log the whole drive with *.
3.) Invoke [Alt+C]ompare.
4.) Specify the source dir either by typing or pointing to it with F2. Once you have done this this path is stored in history and you can assign a(nother) letter to this path so that a macro can retrieve it from history directly for future use.
5.) Tag file that are [U]nique but *not* [N]ewer!
6.) [(Ctrl+)B]ranch into file list.
7.) [Ctrl+D]elete unique files.

If you put all this into a macro you only need to type F12 and recall the macro from the history list. But caution! Make backups on you data before trying out such a macro which deletes potentially deletes a large number of files. Maybe you only use the first part in a macro and do the cleanup of no longer exisiting files by hand from time to time.

Jürgen.