you could
1. keep the linux that's already installed
in which case you should ask your son about the password
for root
then you login as root and create a new user
yes, there's a way to reset the password
if you have a floppy drive, you can create a rescue disk
you can download one from here
http://www.toms.net/rb/
then boot from the floppy, mount the partition where linux is
located and cd on that partition to the etc directory
there's a file named
passwd
check if there's a file named
shadow
if the answer is yes the file you need to edit is shadow, otherwise
it's passwd
open the file with an editor (vi, for instance) and go to the
line that starts with
root:....:
copy that line below, and precede the original with '#', so that now
it is like this
#root:....:...
root:....:...
the (encrypted) password is all what's between the first
colon ':' (after root) and the next colon
remove all the characters between these two ':' in your second root line
afterwards it should look like
#root:c03m900...:...
root::...
save and exit
then cd to the floppy, umount the partition, reboot (remove the floppy)
at the login prompt type after your typed in 'root' you shouldn't be
prompted for a password
Now you can set a new password with the command
passwd
2. if you prefer to install a new linux you might get
a more recent linux than the one installed but not
too new, especially if you want a graphical interface
you can try
slackware and select xfce as the window manager (kde might not
work on your laptop if you don't have enough RAM)
if you want to try out slax (as suggested below) the more
recent ones won't probably work (they use kde and require
at least 256MB of RAM) you can try the versions 5.something
that have xfce