in my keyboard other key dont function how do I fix it?

how old is it if its say 4-5 years old its dirty and needs cleaned you can start out buying a can of air from best buy or walmart any place has can air. and blow out under the keys. then with the unit off push all the buttons a few times and do another blow out and see if that helps if not you will need a new key board which you can get of ebay for about $20.00 bucks and there not hard to change just a few screws from the bottom of the unit and one ribbon cable is all. they do hide the screws there will be some where the battery goes and some times they hide them under the boots just go slow you can do it good luck