How do i reset my Gateway GT5662 to fact. set

Hello,
i want to know how can i reset my gateway gt5662 pc back to factory settings. i did it before, and i didnt have the cds. but i dont know how i did it. i cant figure out how to reset my PC back to factory default. reason i want to is to erase stuck servers with passwords i cant seem to change. like red alert server thinks its using another 1. but it shouldnt be!!!

i want it like the day i bought it. can some1 help me?