How many burners can a PC support at the same time?

We are a rafting company that sells our photos on cd. Currently we have been simply burning to the one on-board burner. This creates down time while each disk burns. Each burn is a unique project and not a duplicate. Can I hook up 5 external burners to a well equipped PC and burn 5 unique projects at the same time? If it is possible what should the PC be equipped with in terms on memory, processor and anything else? Thanks for the help.
 
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