Do you have Nero installed? I would try to install the OEM version of Nero that came wiht your external dirve. i'm not familiar wiht Napster as a burning program so I can't help. I presume that somewhere in that software setup it is not properly configured to burn cd or dvd data files. Try Nero and let us know. BTW if you are using a an intel mobo and running hard drives in RAID 0, Intel requires that program acceleration software be installed and Nero 6 and Roxio 7 will cause your system to reboot when attempting to burn.
Noli Nothis Permittere Te Terere!!
EVGA 680i, Dual EVGA 8800GT'S (650/950), 4 gigs OCZ DDR2 1066, Intel Q9450 at 3.8 Ghz, Koolance Water Cooled, Dual Plextor16x DL DVD+/-RW. Dual WD 250gb 16mb Cache Sata 3.0. 3DMark06 score = 19,168.