I think it's impossible to delete the "Administrator" user. You might need that account if your computer gets screwed up (or you forget your other passwords) and you can't log on.
Related articles:
http://support.microsoft.com/default.aspx?scid=kb;ln;281244
http://support.microsoft.com/default.aspx?scid=kb;ln;298252
http://support.microsoft.com/default.aspx?scid=kb;ln;281140
http://support.microsoft.com/default.aspx?scid=kb;ln;314412
quote:
If a computer administrator starts the User Accounts tool in Control Panel, the built-in Administrator account may be displayed. This account should not be visible.
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