Problem typing umlaut characters in W2K

User on IBM Netvista PC with Win2000+SP2 is from today surprisingly unable to type umlaut characters (like ?,?).When uses umlaut button (next to’P’on dutch keyboard)and then a letter,two umlauts always appear followed by letter,instead of one umlauted letter.No changes or reinstallation in keyboard/regional settings helped.Same problem is with other keybrd.When using Alt+number combination,bizarre characters appear instead standard letters (e.g. Alt+065 gives a circle).