regarding my problem of cd drive

Sir, my system i.e I ball piano 99,gigabyte motherboard. i have recently changed my OS to windows 7.my system is not recognising the cd which i am inserting.pls can you helpme, one thing i have forgotten ,2 days back i have reported problem to my bro, he came and changed the bios settings to first boot device CD ROM,second boot device CD ROM,third boot device CD ROM.pls can you find me a...