Hi Leo,
What OS?
In Windows XP, you'll find the on-screen keyboard under "Programs > Accessories
But IMHO, it's not helpful to install different keyboard layouts for different
(Western) European languages.
It's simpler to define some custom keyboard shortcuts for the couple of special
characters you need.
Most likely, some sensible shortcut(s) already exist(s):
Select the character, open "Insert > Symbol": It'll show existing shortcuts (...
if several different shortcuts already exist, you can see all of them if you
click on "Keyboard shortcut...").
Or buy an International keyboard, and learn the existing AltGr shortcuts, which
then work in all programs, not just in Word.
Greetings,
Klaus