Cd/dvd gone from pc

Hi, My cd/dvd drive has dissapeared and I don't know how to get it back. I've lost my start up disc, I don't think I have ever registered my computer online, I've tried all of the above methods except for installing a new driver. I don't show any cd/dvd on my device manager and I don't show an upper or lower filters box. I'm running a gateway model GM5472. My device was working fine now it's not. I had also intalled windows updates. Since I don't use this device everyday I'm not sure how long the problem has lasted but no more than a week for sure. I don't know if it had something to do with Adobe as I had to download this to view an interactive cd/dvd for my college class testbook, I need help because it's very important that for school reasons I get this problem solved. I don't have any money for an expert techie, please can someone help me? I've also just uploaded firefox, have been trying anything to correct this problem.