Sharing. You haven't mentioned setting up sharing on any of your hard drives or printer. I've got a main PC, another PC and laptop, The main is cable connected to a D-Link moden/router and the other PC and laptop D-Link wireless connected via the router.
From any computer I can get into and rummage about [open, close, delete, move, etc] in any other hard drive and print from any computer to either printer (laser and inkjet).
Double click on 'My Computer'. Right click on the hard drive letter and you will find a 'Sharing' button. Same for printer [control panel - printer - right click on printer - hit the sharing button]. You have to set up each hard drive and the printer to share.