Asus Wireless Router - No Password To Protect Internet?

I have an asus wireless router the router lost connection for a few days and when Internet came back there was no password to protect Internet and was just basically open access. The computer which all the Internet setting are on went away for repair. When the man brought it back after backing up the computer I asked him to put the password back on the Internet. This he has done. We entered the new passwords on our iPhones and they connected and worked no problem. Then we tried to do it with our laptops but they won't connect. Phoned the bloke back he said we had to get the laptops to forget all the old settings for the router and it would on take five minutes but he never told us how to do it.