If this line is missing or remarked out, add it or remove the REM from the front of the command line. Not all CDs are made to the same quality standards. Some CDs with a lot of artwork will vibrate due to the weight of the ink or paint on the CD causing the CD to be out of balance. This will allow the CD-ROM to slow down when it detects vibration. Another common problem with CDs is scratching.
Scratches cause the laser in the read head to refract, causing a read failure.
CD scratch-removal items are usually available at your local computer retail outlet store. Another common problem is that the CD-ROM spins up and down frequently, even when accessing the drive. This is a feature of the firmware on the CD-ROM used to conserve power. The CD-ROM is functioning properly. Change the setting to Variable.