Your USB CDRW probably writes to CDRW discs at 2x or 4x (no faster). A 650 meg blank CDRW disk contains as much as 74 minutes of digital music. If your burner is 2x it should erase (rewrite to blank) in half that time (37 minutes). With 4x, a quarter that time (18 1/2 minutes). Obviously, something seems wrong. However, since CDRW discs are erasable, even if the erase got screwed up you should be able to just erase again and fix the disc itself.