Burnt Cd Not recognised

I am having trouble with some burnt cd’s. When a programme asks for disk no 2 etc and I have put it in the drive the programme keeps asking for it as if I havn’t put it in.
This is happening consistently.I burn at the lowest speed and have tried different brands of cd’s.I was wondering if I have to use a different setting. I am a recent computer user and don’t understand a lot of the terms the burner programme uses.I have asked Nero for help but they don’t want to know. I am using windows 98.