Archiving messages to a .PST is considered an offline folder at this point. for you to be able to click and drag active items to the archived PST, you will have to have the archive folder opened within your Outlook client.

Renaming the current Outlook data file will force Outlook to create a secondary PST or OST. This method has the best results if you are working with an exchange service.

(not familiar with carbonite)

Hope this helps.