Credential roaming is an enhancement to roaming profiles. Rather than roaming large amount of data (as invariably happens with roaming profiles), only certificate and Data Protection Application Programming Interface (DPAPI)–protected credential information is roamed between computers.
Windows XP Service Pack 2 clients with the Credential Roaming service update applied and Windows Vista clients can utilize credential roaming to ensure that software-based certificates are available at any domain member computer where the user logs in.
Credential roaming helps prevent the following:
Excess enrollment of signing certificates for users with multiple computers. If a user logs on to more than one computer and is eligible to receive certificates ...