The laptop needs to be configured in Ad-hoc mode either using XP built in wireless settings or using a utility that came with the wireless card. If you are using the utility, you need to run that. If you are using Windows XP wireless settings, here are the steps:

1. Open the Network Connections folder.
2. Right-click the Wireless Network Connection icon and choose Properties.
3. Click the Wireless Networks tab.
4. Add the SSID (network name) that you are using on the other computer.
5. Click the Advanced button.
6. Choose the Computer-to-computer (ad hoc) networks only option.

If you are using the utility that came with the card, you need to check with the manufacturer's instructions.