check mac model and specifications.

http://www.everymac.com/ultimate-mac-lookup/?search_keywords=MacBookPro5%2C1

it is pretty good site.

http://www.everymac.com/systems/apple/macbook_pro/stats/macbook-pro-core-2-duo-2.4-aluminum-15-late-2008-unibody-specs.html

this one easily check the maximum memory.
http://www.everymac.com/systems/by_capability/actual-maximum-ram-capacity-of-macs.html