Microsoft Office 2003 SP3 Breaks Outlook Forms (.oft)

If you have upgraded the standard install of your company's PCs to Office 2003 Service Pack 3 (released Sept 20th) then you may be having some problems with Outlook Forms.

The error message "The custom form could not be opened. An Outlook form will be used instead" will appear when you attempt to open any customized Outlook Forms saved as .oft files (such as forms stored on a file server or shared drive).

The solution to this problem is to change two entires in the registry which disable the new security properties available in Office 2003 SP3. These two options will revert Outlook 2003 SP3 back to it's SP2 form security settings.

Create the following keys in HKEY_CURRENT_USER\Software\Microsoft\Office\11.0\Outlook\Options\Mail
"AllowTNEFtoCreateProps"=dword:00000000
"AllowMSGFilestoCreateProps"=dword:00000001

This is especially helpful because Service Pack 3 cannot be removed, you must uninstall all of Office 2003 and reinstall.