Thanks for explanations. Everything is very clear now.

I though to have been pivoted to knoppix on sda6 (which was made root by the system).
This can be done and is ok. From what I read, you were successful. Pivot from Knoppix CD to Knoppix-HD on sda6 is probably easier and presents fewer problems than what I did which was to pivot from Knoppix CD to Debian Etch. Now all you need to do is copy your Debian Etch /home/Francesco to /sda6/home/Francesco. Hopefully you will find the contents (your molecular mechanics package) on sda6/home/Francesco after pivoting.

Continuing on my ME above, I intended to install packages on knoppix-HD on sda6 partition, either in /bin or in my home. It was unclear if I had to make any persistent image: I though NO, because everything should be on my external HD.
Ok, installing packages on Knoppix-HD on sda6 can be done. The only thing to remember is that not every Deb is compatible with Knoppix. If you install the wrong package, you could cause problems to the Knoppix-HD on sda6. Most people who have problems after hard disk installations met problems this way. Best to test beforehand. If you install to Knoppix-HD on sda6, no need for persistent image now, because the programs are on sda6.

Is any risk of damaging Windows and Mac operative systems on running pivot knoppix as above?...............I meant Windows and Mac as the only OS on the computers that I'll have access to during my travel. I intend(ed) to put the live knoppix CD on their CD player, and my USB/Firewire HD on their usb or firewire port
Ok, little or no risk, if you only use sda6 and the CD, and don't mount the disks belonging to your hosts. Knoppix will never mount any disks without your command. You can also safely mount your host's disks to read-only in order to read data. Just remember never to try to write to an ntfs formatted disk.

Also, a notebook normally delays the travel because police wants to known if there are any bombs inside. It was so in the past. I imagine it is worse today. In addition, I have so many things with me, that a knoppix disk and a few ounces HD is a better perspective that a notebook.
You are right!

The South Seas are no more those of Stevenson (unfortunately). Heavily populated, universities (I am going to visit them again). They have even plans for high-speed cable. Anyway, internet works as anywhere. The very reason to bring my system with was to be able to do want I may need to do. Example: modify my CD-recorded ppt=saved conferences because I knew something I was not aware of, so that my CD would be ridicoulously outdated (even there today the conference are through a ppt, not live conference; you can not find anymore an overhead projector even there).
That's good news. I don't think you will have much problems doing what you want to do. With internet, you can keep in touch with home if you encounter problems. Secondly, if there are universities, there is a good chance they may even be using Linux and OpenOffice (many universities do), so you can use theirs.

Regards and Good Luck.