Problem with upper function and special characters

Hello,
I have postgresql-7.4.3-1 in windows xp professional sp1 and cygwin.
Postgresql was installed with "--locale=es_ES". parameter

My problem is with the upper function. When I use it with special
characters like áéí, it doesn't convert the case properly.

Ej:
select upper('a');
result is: A (OK)
but ,
select upper('á');
result is: á (It should be Á)

I'd really appreciate any help.

Thanks,
Gerardo.