If your SunCD 4 drive cannot read a compact disc, you may have a dirty disc.
To clean the disc:
Use a soft, clean, lint-free, dry cloth.
Clean the non-labeled side of the disc.
Wipe the disc radially from the center to the outside.
Do not use solvents like benzine, paint thinner, antistatic aerosol spray or abrasive cleaners to clean compact discs.