Hello I have been using an NEC 3550a disc drive for the last couple of years and it had been working great.Recently though it has stopped recognizing dvds. I can still play/burn cds and can even still burn dvd files on my hard drive but when i put a commercial dvd in the tray it spins and the little cd loading icon symbol comes up next to the mouse clicker and then nothing happens. I have updated firmware and deleted upper and lower filters and i am just wondering if there is anyway to check if this is a software or hardware problum. I find it strange that i can still burn dvds just not play them?