Is the router's Wireless Access Point switched on? There may be an option in its wireless settings for something like:
- B only (for 802.11b only to connect)
- G only (for 802.11g only to connect)
- Mixed B & G (to allow either type to connect)
Also check that the router is set to broadcast its SSID, or it won't be found when your laptop scans for "Available Wireless Networks".