Error with Unread Mail folder (Outlook 2003)

[David Smith]

Outlook 2003 is running fine, but if I try to customise the Unread
Mail folder (which currently has only ticked my Personal Folders head
folder -- it isn't looking in any of the subfolders), I get an error
message which reads: 'The operation failed due to a registry or
installation problem.'

Have tried restarting Outlook with 'Outlook.exe /resetnavpane' from
the command line -- no change. Any ideas?

Thanks.