Same here, a couple year ago I had 9 hrs layover. So, i had my baggages checked right through, I only had a carry on, I place it at the aiport storage for a small fee. I then took the express train into town for a scenic tour, had lunch and back to the airport.
Check out the Hongkong International airport and you will find the baggage storage. If you want to do transit tour of Hongkong, check out its website at discoverhongkong.com.