I purchase the downloadable version of Red Hammer. How can I make a backup copy?

Unlike the OFP Gold and Gold Upgrade CDs, the 35MB file that you downloaded to pay for and install the Red Hammer Campaign would require you to purchase it again every time you run it.

That should hardly be necessary, however. Red Hammer consists of two essential files plus the Prima game guide PDF file. So all you need to back up is the following:

\OperationFlashpoint\OF_PRIMA_xxx.PDF
\OperationFlashpoint\Addons\Voicerh.PBO
\OperationFlashpoint\Campaigns\REDHAMMER.PBO

Once that's backed up, you can safely delete the 35MB Red Hammer purchase and download file you originally downloaded from Codemasters.