Funny Characters on Win98SE

....any ideas on this would be appreciated!

Sometimes I have to write reports with Word in Spanish and Portuguese and i need to type characters like "??o" or "f?" or even "? - ? - ?" etc. Anyway, I use keyboard combinations to make the typing a lot fastet but, somehow nowadays, everytime I try to insert these characters the machine types out: "?~~ao" or "f??o" or "??a........

Any idea how I can get it back the way it was,...

By the way, I did not change anything on my machine, but other people have access to it and they have used it,....