Can not connect to my wireless secured network

I have  the D-link router DI-624 .I tried to connect my new laptop computer Samsung nc10  (windowsXP SP3 operating system) to my secured ( has yellow lock icon) wireless network .I was unable to do it but the computer automatically detected and connected to the unsecured network with  a very weak signal. When I tried to connect to the  Internet I received message ''page can not be displayed.Cannot find server''Samsung technical support technician  after helping me to install a new driver , which did not help, advised me to reset the router and update the firmware.I do not know how to do it ( update firmware)  and whether it will solve the problem .I Have  WEP and at certain point when I tried to connect to  my secured network I was asked to provide the key which I did but it did not help. I would appreciate your help.