2007 MacBook Pro 3 hd drives, 1 screen replaced: what's recyclable

I’ve replaced my 2007 15” MacBkPro w 3 hard drives, 1 screen, maxed out the memory to 4 G, replaced the power cord, DVD drive.

it’s time for a new HD but maybe too late? what can I do w it at this point? I can only upgrade the OS to El Capitan. Can’t run HD video. If I buy a new NB what do I do w this one? what will happen to it? who can use the parts if no one is using these NBs?