Hang on a sec, just thought back to your OP.
You only have a modem right? There for, to get more than one PC on the network, you will need a router.
A modem on its own cannot handle more than one IP address. when you connect the modem to your PC directly, the PC takes on the IP address of the modem, the modem is just shuffling the bits back and forth. The PC is part of the internet directly.
When you have more than one PC, you have a private network, that needs to be connected to the internet (or any other network). This is what a router does, it routes data between to two.
Then there us NAT, Network Address Translation. This give you the ability to have multiple PCs on your own network sharing the same IP address given to the Modem (or router if it has a built in modem, like with ADSL) by your ISP.
So ignore the comment about a switch or a hub, you need a router. So you may as well get a wirless one. if it doesn't leach to your room, then too bad, but you would still be able to use your laptop in the lounge or kitchen or something if you wanted.