Currently Being ModeratedMay 31, 2012 7:22 PM (in response to Athan Katsos)
The headphone jack is your combo headphone/line out. You use a mini plug on the MBP end and, depending on your external amp/speakers, either a mini jack or a pair of RCA jacks.
PS. Your OS X level can't be 10.3.7 ... MacBook Pro's were first delivered with OS X Tiger 10.4.