i think you're confused about multi-session recording.
if you already copied the songs off the CDRW disc onto the hard drive of the Xbox, you can safely erase the CDRW, burn the new songs onto it and copy them to the Xbox.
no need to write everything in bold.
One Ring to rule them all, One Ring to find them,
One Ring to bring them all and in the darkness bind them
In the land of Mordor, where the Shadows lie
M.C. Escher - Reptilien