How can I hard wire my pc with cat 5 cable ?
You need to wire your house first. That is, run a CAT5e (or CAT6 - don't use CAT5) cable from a Ethernet port on your router on the 2nd floor down to the first floor. Then what I would do is connect the 1st floor Ethernet cable to an separate Ethernet switch like this
. Then connect your computer to the switch. The switch will allow you to connect multiple devices (printer, network storage, other computers) via Ethernet to your network. And being a 1Gbit/sec switch, it will not hamper performance.