Empty dvd disk after successfull burning

when i burn dvd disk with nero, i get completed succesfully. but when i try to see in windows explorer the content of the disk, i dont see a thing. when i see the properties of the disk, i get free space=0, used space=0.
this thing happens when i use the option “make data disk” (for pictures) and also when i used the option “burn dvd video files” (for movies). if it’s matter, the burning has contained files in number of folders.
but when i took the dvd to another computer or dvd, i saw the files that i was burning.
if i go to the command line and i try to see the content of the dvd, i get “the volume does not contain a recognized file system. please make sure that all required file system drivers are loaded and that volume is not corrupted”.

when i burned to cd, i didn’t see a problem.

my os is xp version 2002
driver od dvd is nec dvd_rw nd-3550a
nero 6

anyone knows whats the problem?