Are you making a copy of another physical CD? If you are doing that and use a regular CD rom drive to read the source CD while the burner burns onto a blank, then maybe your regular CD-ROM drive can't extract data/music at the full speed of your burner. My brother's PC has a 32x CD-ROM drive and a plextor 12/10/32, it's only able to copy a CD from the CD-ROM drive at about 4x or 8x depending on whether it's a data or music CD being copied.