On the Exchange Server 2003 server launch Exchange System Manager. Navigate to the Public Folder store on the Exchange Server 2003 server.
Right-click the Public Folder store and select Move All Replicas.
Choose the Exchange Server 2007 server in the drop-down list and click OK to continue.
Click OK to clear the information message and begin the move.
When the Public Folder Instances folder for the store shows no items the public folder migration is complete.