Live booting from a 512 MB RAM system then take an image from it?

Someone loaned me an--old--laptop for a few months (that hasn't been used for a couple years) which has a deprecated non-*nix on it. I doubt the loaner would want the system restored if I managed to install a secured linux on it, but just in case I'd like to make an image of it. The system has a P3, 512 MB RAM & 40 GB HDD, more precisely it's a Dell PP01L (Latitude C600). I haven't established yet if it can boot from USB, but it has a DVD player, a (tested) USB port and I have blank DVDs, an ext burner and ext HDD.

Which distribution and software would you recommend to live boot on the 512 MB RAM P3 to take an image from its HDD on a 4 TB ext HDD?

Thank you kindly