When using Outlook to send email errors may occur, including:
Can not send email directly from Word or Excel
Attaching a document into a new message results in error message of “Word unspecified error” or “interface not registered error 0x80040155”
To fix: Close all office applications and go to Start menu, Run (or use Windows key + R) and type
Regsvr32.exe %Windir%\System32\Ole32.dll
Press Enter or click OK. Restart Outlook.
Note: This fix also works for the error "Microsoft Word is set to be your e-mail editor. However, Word is unavailable, not installed, or is not the same version as Outlook. The Outlook e-mail editor will be used instead. An OLE registration error occurred. The program is not correctly installed. Run Setup again for the program."
More Information
You receive the “Interface not registered” error message when you try to send or to save an e-mail message to the Drafts folder in Outlook 2002
Problem: WordMail Busy or Unavailable
You receive the error message "Word is unavailable, not installed, or is not the same version as Outlook" when you try to create, to edit, or to reply to an e-mail message in Outlook 2003
"An OLE registration error occurred" error message when you open an mail that contains embedded Lotus Notes document links in Outlook 2000
You Receive a Warning Message or You Cannot Start Outlook on a Computer That Is Running Small Business Server and Exchange Server