If it's not the laser then it's very likely either the CD-Rs you're using or the burner. I know from experience that some brands of CD-R will not work at all. I also have a burner in my main PC that can't reliably burn games that the Dreamcast can read. I use an external Samsung drive instead. If you have a different burner you can try, I would try that first. If that fails, get some new CD-Rs. Unfortunately it's a bit hard to find a brand that will always work. Even among certain brands like Sony, Memorex, and Verbatim, they usually have different manufacturers making the discs so they're not always the same.