Secure network in an apartment complex

Hello, I have 3 machines on my LAN, and would like to secure them. The apartment complex I live in provides Internet access from the landlord's router, this is shared with 15 other complete strangers.

I'd like to keep them off my LAN. I am not allowed to use a wireless router as that's against my rental agreement.

Currently all I have is a switch plugged into the feeder cable, my machines into the switch, and they all obtain IP etc from the DHCP server on landlords router.

One of my boxes has dual gigabit ports, and a wireless card acting as an AP for my laptop. Is there a simple way of plugging feeder cable into one, completely securing it, then attaching other NIC to the switch to provide secure access both wired and wireless?

I forgot to mention, all machines running Windows 7 Home Premium, and all network connections set to Public. I want to use Homegroup on the LAN, and share my printer - just not with everyone else on the router.

Any ideas much appreciated.