I can use windows media player to make a copy of a commercial music cd to play in a stand-alone CD stereo system, using CD-R disk. Why can't I use a CD-RW disk?
Just curious.

Because the CD/RW discs are different.  Newer and more sophisticated CD players (like many of the newer car CD players) can play CD/RW discs as well as CDs with computer music files on them.

Many thanks yr reply Ray, glad it wasn't my ineptitude!!