Well, now we know you can boot a LiveCD. ...
Well, now we know you can boot a LiveCD.
Bad news. If you install a new distro, you will lose whatever software you had on the old one. You could keep some stuff if you reparttion the disk drive by resizing the current partition but that isn't the easiest for a newbie.
Good news. Linux software is free. So if you know the names of the education apps you had, you can install them in the new distro. Instead of Slitaz, I'd suggest you google "Edubuntu." That is a special Ubuntu edition for educational use.
If you still want to install Slitaz, click /Menu/System/Slitaz Installer. It will then ask where you want to install. Typing "hda1" will use your current partition, overwriting what there. To keep your current Ubuntu, you would have to repartition prior to running the installer. If you need help with that, let me know.