Just bought second hand router belkin 54g trying

The WPA encryption key is configured in the wireless router's settings.
Since the Belkin is second hand and most likely the default password has been changes and you won't be able to get the encryption key unless you reset the Belkin back to the factory defaults. To do this :-
Power up the Belkin, press and hold the RESET buttom for exactly 7 secs.
Then to configure the wireless router - follow these steps :-
1. Connect a LAN cable from your computer to the Belkin wireless router.
2. Open IE browser and enter the Belkin's URL configuration IP address.
http://192.168.2.1 the password is blank - just press Enter.
3. Change the admin password
4. Go to the wireless settings and change the default SSID and turn off SSID broadcast.
5. Setup encryption key the strongest is WPA2 (if not then WPA).
6. For further security measures - turn on MAC address filtering and enter the MAC address of the wireless cards on the computer/s you want to connect to this wireless router.
7. Record the settings you have made and keep it in a safe place and Save the settings.
8. Configure the wireless cards on the computer/s and PS3 with the SSID and encryption settings of the router.
9. Remove the LAN cable between the router and the computer then the computers should be able to connect to the router.

the old owner of your router know the wpa code he/she inputed you must ask him wat is the wpa code since you are now the new owner you shold chnage also the old wpa code to new one....