See Location of other Outlook Add-In registry values.
0 - Never deploy forms locally.
1 - Only deploy forms when there is no Organizational Forms Library available (default).
2 - Always deploy forms locally.
3 - Always delete Enterprise Vault forms from the user's Personal Forms Library.
Specifies whether, when the user starts Outlook, the Enterprise Vault add-in determines whether the Enterprise Vault forms are installed or need updating and then adds or replaces them as necessary.
This enhancement is required to enable Enterprise Vault to store forms in each user's Personal Forms Library in an Exchange 2007 environment when there is no Organizational Forms Library.
See List of Outlook Add-Ins registry values