Instead of using Live CDs or DVDs, I'd like to carry with me my Linux system (complete with all my preferred tools and programs) on an external USB hard drive, thus being able to achieve much more performance and the possibility of saving things on my drive without touching the content of the computers to which I connect it.

The idea is:

I get to the computer I have to work on (for example inside a customer's office), I turn it off, I connect and fire up my USBdrive, I turn on the computer, I go to the BIOS settings and set the external USB drive as the first boot device, I get inside "my" Linux system and use it as I need, WITHOUT any kind of unwanted writing action on the internal drive(s) of the computer. When I have finished I quit Linux, turn the computer off, disconnect the USB drive, turn the computer on again, go to the BIOS and set the boot order as before.

Looking around in forums and documentation, I found out that this task seems to be quite complicated, due to mbr and bootloader configuration issues. I found many suggestions on how to make the above possible on a single computer with stable hard disk configuration, but no mention at all about using the USBdrive Linux system on any computer (equipped with a not too old BIOS...) without changing in any way it's hard disk content.

So a few questions came up. Can it be done? How?

Thanks a lot for any help

when you can boot from usb, there should be no problem.
I have puppy on usb, works great on many computers.
it loads completely in RAM, and you have access to the hard drives of the host computers if needed.

have you looked at the pendrive Linux site ?

http://www.pendrivelinux.com/