> How to keep all files?> (Why it is overriding?)


Humm, httrack will have troubles handling naming if you are using the same
directory. Basically the cache will be reused, and httrack will probably wipe
previous file(s)

Why don't you mirror all files at once ?
httrack\httrack.exe <http://localhost/a.html?1> <http://localhost/a.html?2>
<http://localhost/a.html?3> -N %M -K -O myfolder/  -v

(You may also want to move/backup the files each time as an alternative)