“Mail is not Installed on system” Problem

Using MS Word (Office XP Pro)
on Windows XP Pro SP2
Default email client: MS Outlook 2002 (not OL Express)

The toolbar button:
“Send to Mail Recipient (as Attchment)” is disabled in MS Word.

I think this is because Mail has somehow become unavailable. Running a simple VBA procedure such as:

Public Sub MailDocAsAttch()

Options.SendMailAttach = True
ActiveDocument.SendMail

End Sub

brings the error message:

Runtime error ‘4605’
The SendMail method or property is not available because mail is not installed on your system.

I compared the installation with a similar working installation where the problem does not occur. There were no differences in the Office applications’ settings and Outlook 2002 was the default email client on both.

How can I restore mail? Any help would be greatly appreciated.

Thanks in advance.