Well there are ways to get around buying a wireless router, but a wireless router is cheaper than 2 wireless cards, or even a wireless card and a 2nd NIC for 1 of your wierless cards and it's a lot less hastle. It would be best to go:
Modem
|
wired PC - WiFi Router - Wired PC
Wireless Laptop Wireless Laptop
Then you'd just go "Start" > "Control Panel" > "Network Setup Wizard" and follow the steps.
You can pick up a decent 802.11B Wireless Router for around $30 if you know where to look (which is all you need for online because I doubt your connection tops 11mbps anyways
) and an 802.11G router for around $50-$60. If you REALLY want to get those speeds up there you COULD get an 802.11a/i/n/z router but atm it's not worth it.