I've checked the option for turning on Desktop Alert on Outlook 2007. The user has POP3 Inbox and IMAP Inbox in her Outlook. E-mails come in by default to IMAP inbox. The pst file file for POP3 is selected as the "default data file". (Outlook won't let me make IMAP pst file as the default data file. It greys out "make default pst file" for IMAP pst file.) The Desktop Alert won't come up when new e-mails arrive. Is there a fix? The user is on Windows 2K Pro.

Have a look thru the Outlook 2007 Solution Center for a possible fix.
It's a great resource.