I assume that your PC is connected to the router via an Ethernet Cable? Which is why it works. If you connect the Laptop via a cable, it will work too.
To get WiFi working on the laptop, first press Start, Connection to, Show all connections. The Wireless Connection should show Enabled. If it shows disabled, Right click and select Enable.
The other thing that can cause this problem is interference from other WiFi networks and/or devices that chuck out lots of EMI. You could try fixing the former by using a free utility called inSSIDer. The latter is usually a problem for professionals - such as me.
T, February 2010