CD Rom Trouble

My cd rom has only been reading certain disks lately. When I try to open a program on cd I often get the message: Device not ready. Every so often the cd will autorun and everything will be fine. I tried to scan the cd rom, but I got the message that the cd rom is locked by a utillity. I have no idea which utillity or how to find out. There is no resource tab under properties so I have nothing to learn from there. I am running windows 1998 on a pentium II with 320 mb of ram. The cd rom is a sony cdu-701, with a generic driver. I have several utillities loaded like: Nuts and Bolts, Sandra, Norton Anti Virus. I tried to download and run the dos utillity amidiag but it doesn’t seem to work. Please help.