So you went down to the basement to unearth your old CD collection, only to find your disks speckled with mildew? Don't worry--mildew cannot grow directly on a CD, only on the dirt or residue on a CD's surface. Remove the dirt, and your CD will come clean, too. You will need several soft, lint-free cloths or cotton handkerchiefs to do the job right, switching cloths often to make sure that the mildew is not getting spread around. The mildew needs to be physically removed, not just killed, for your CD to play right. Here is the safest way to do it.
Clean excess mildew off the CD with a soft wet cleaning cloth. Wipe in straight lines from the center of the CD to the edge. Never follow the ridges when cleaning a CD, as that will only spread the dirt around. It could also scratch the CD.
Rinse the CD under lukewarm water and let it dry.
Repeat the cleaning step if mildew is still clumped on the surface, adding a bit of dish soap to the water. Rinse well and dry the CD.
Moisten a soft cleaning cloth with rubbing alcohol. Work your way around the CD, wiping from the center to the edge, until the entire CD has been covered.
Allow the rubbing alcohol to air dry, to give it time to kill the mildew. Rinsing the alcohol off could stop the process.