Paint the CD with white paint on both sides. Let dry and apply a second coat.
Paint eyes and a mouth on one or both sides of the CD in black paint. [When the wind blows the ghost about, the backside of the CD will become visible.]
Run the string through the center hole and knot ends together. Cut the ends off close to the knot.
Suspend the CD from a shelf or cabinet door so you can glue on the streamers.
Cut several layers of white tissue paper in 1" wide strips. Example has 12 strips on each side.