You can save your custom Outlook categories by exporting a registry key.
Outlook 2000HKEY_CURRENT_USER\Software\Microsoft\Office\9.0\Outlook\Categories
Outlook 2002HKEY_CURRENT_USER\Software\Microsoft\Office\10.0\Outlook\Categories
Outlook 2003HKEY_CURRENT_USER\Software\Microsoft\Office\11.0\Outlook\Categories
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