Even if I changed the limit speed to 20 MB/s (20000000 B/S) it does not
download at more than 70 or 80 KB/s (it takes more than an hour to download
500 MB ).

The server is quite fast, now has low traffic, but it has been able to serve
huge charges in the past.

May be there is some limitation in the server of forum software for a single
IP?Is it a limit of htttrack?
We are using WinHTTrack (last version from your site) and trying to archive
our huge forum that works under VBulletin 4.

Thank you