I tried Outlook 2007; I went back to Outlook 2003 by uninstalling 2007, then
using Add/remove programs in Windows XP SP 2 to "change" my Office 2003
installation by adding Outlook 2003 back in. Unfortunately, now when I click
on an email link on a web page (a link to MailTo:recipient), I get the error
message "Could not perform this operation because the default mail client is
not properly installed." When I close out this error message window, I get a
cascade of 20 or 30 blank web pages or pages reporting navigational errors.
How can I restore the functionality of the MailTo links?

I should note that I have "repaired" the installation using the Add/Remove
Programs listing for Office 2003; and I found an article in the KnowledgeBase
regarding this error report but after created a URL:MailTo entry in File
Types, and specifying the program to use, it still didn't work.

Kurt wrote:

I tried Outlook 2007; I went back to Outlook 2003 by uninstalling
2007, then using Add/remove programs in Windows XP SP 2 to "change"
my Office 2003 installation by adding Outlook 2003 back in.
Unfortunately, now when I click on an email link on a web page (a
link to MailTo:recipient), I get the error message "Could not perform
this operation because the default mail client is not properly
installed." When I close out this error message window, I get a
cascade of 20 or 30 blank web pages or pages reporting navigational
errors. How can I restore the functionality of the MailTo links?

Use COntrol Panel's Folder Options applet to fix the MailTo file type
association.
--
Brian Tillman