Spell Checking 'Subject' line in Outlook, not with US English - How do I do it?

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Is there any way to change the spelling dctionary that Outlook uses to spell
check the 'Subject' line of an e-mail?

I have set Outlook 'Tools' 'Language' to Australian English and Outlook uses
that for the body of the message, but the setting is ignored when Outlook
checks the spelling in the 'Subject' line. It uses US English.

I would ideally like to make Australian English my default for the entire
Windows installation and I thought I had done so by setting English
(Australia) in the 'Regional and Language Options' and removing US English.
One would really like to see the operating system store configuration data
such as regional settings, paper sizes, etc, in one location and have all
applications use those values. This does not seem to be the case in
practice. 'US English' and 'Letter' paper appear at all sorts of unexpected
times. Ideally, I think XP should have no default setting for locale and
should ask for it during installation. All applications should then use
those values.

Hope someone can help with my question?

I am using Windows XP Professional 2002 SP1, with Outlook 2002 SP1.