You can install any Debian-Linux or ubuntu on any old or new system very easily.
If you wanna install from within other os, you can download a small file, from pendrivelinux.com which is win executable and then it will take care of the installation and you will be guided step by step.
If you can download a Linux distro iso file, you can burn it as burn image to disk and your bootable CD is ready for the tour... make the cdrom as first boot in bios and enjoy without installing the operating system.
you can save the Environment also by installing Linux into old working computer.
Especially if you would like to donate your system to a poor student, its the best way to safeguard your old data too.