DVD-R Disks?

I recently bought a Dreamcast second hand (manufacturing date August 1999) and I'm trying to get games on some CDs I have, but it's not working. I'm following the instructions in the "getting started" sticky but they aren't helping. Is it because I'm using DVD-R disks?

I'm no expert on the Dreamcast but you need to use CD-R disks as DVD-Rs don't work on it.

Thanks for the reply. I was about to be really frustrated