Select Use WPA-PSK Encryption.

In the WPA-PSK Encryption Key box, type a pass phrase (also known as Pre-shared key) of your choice. The pass phrase must consist of 8 to 63 alphanumeric characters or 64 hexadecimal characters (characters from 0 to 9 and from A to F).

In the WPA-PSK Version list, click the WPA-version of your choice. Following options are available:

WPA2:
WPA2 is the most secure version, but not all wireless clients already support it. Before you select this version, make sure all of your wireless clients support it.

WPA+WPA2:
If not all of your wireless clients support WPA2 or you are not sure if they support WPA2, we recommend you to choose WPA+WPA2. Wireless clients that support WPA2 will use WPA2, the others will use WPA.

WPA:
If none of your wireless clients support WPA2 choose this option.

To use WPA2 on Windows XP SP2 you first have to install Wi-Fi Protected Access 2 (WPA2)/Wireless Provisioning Services Information Element (WPS IE) update. You can find this update on http://support.microsoft.com/kb/917021.

Click Apply.

Configure your wireless client(s) with the same settings.