Thanks,

in that case I'm just gonna use one of those windows programs you mentioned
inside VirtualBox. This means that I need to restart the process however. But
better now than waiting even longer and lose even more time ... so: thanks for
that tip :-)

A suggestion: the signal SIGQUIT could be used to tell httrack to go into the
'finish pending downloads' mode.
Also a hts-finish.lock file should work ...

Thanks,
   Frank