Cd and dvd copying

I have a HP media center desktop computer with Windows Vista Home Premium.
Sometimes, not always, when I try to make a data disc, I get a message that the cd or dvd that I am using is not blank. I have put in new blank discs or a rewriteable disc that I have erased or formatted. The software on my computer is Roxio. It works fine on other features that it supports.
Can anyone help me and tell me what to do? I must be doing it wrong. I am not new to the computer, but I don’t burn discs that much to be well informed.