> My friend wanted his father to be able type £ and € and accented French
> characters.
> I found that if he used the US-International keyboard he could type all
> of these chars.
US Intl Layout
see also for other Windows KB layouts
> £ = SHIFT+ALTGR+4
> € = ALTGR+5
AltGr is just the same as (Right)Ctrl+Alt.
ZTW help has a section about AltGr functions for a couple of non English KB layouts.
> Then I noticed that sometimes when I typed the " it didn't work and
> then it entered it twice.
dead key as described in your follow up post
dead keys are completely different/independent of AltGr combos.
the layout I'm using (Swiss German) has dead keys for generating letters with ´`^~¨ accents *and* AltGr combos to access "US characters" like @#|¢[]{} and €.
using those keyboard features is so common for non English speaking users we don't even think about anymore.
greetings, andreas