I have a Model Number

I have a Model Number F5D8233-4v3, Belkin N Wireless Router. This router has been working great until a friend of mine came to my house and wanted wireless online. His computer asked for a security number. I looked on the bottom of the router and gave him the number 59551607. He entered the number and ever since then my computer will not hookup through the wireless. Before, there was no security icon lit on the router, but now it is lit. Also on my wi-fi there is a security icon beside the Belkin_N_Wireless network. It says... "The settings saved on this computer fo the network do not match the requirements of the network. What can I do to fix this?