Box serial number doesn't match up with serial number in 'system info'

Hello, I'm trying to figure out what serial no. goes with my CS5. I'm in an office where we've kept the boxes with the serial numbers, but there's 4 or 5 boxes and I don't know which one goes with my computer. I've looked in photoshop's 'system info' and there's a place where it gives me a 19 digit serial number, but it doesn't match any of the boxes we have, which all have 24 digit numbers. Is there anywhere else I can look to find my computer's CS5 serial number?

Thanks