Track-At-Once or Disc-At-Once? Use track-at-once for creating multisession data CDs. The drive initiates the disc's lead-in, burns the data, then goes back to the lead-in to tell the disc where the files are stored (similar to the way a file-allocation table works). The drive then completes the process by writing the lead-out for the disc, which identifies where one write session ends and the next begins. This requires a lot of overhead, so you'll get less than 700MB of space for data on the disc. Roxio's Easy Media Creator chooses the correct session automatically; Nero automatically selects track-at-once, but it does give you the option to change it--so leave that setting alone.
Use disc-at-once if you're writing to the disc one time. With disc-at-once, the drive writes all the data in one fell swoop and automatically finalizes the disc. This is useful for maximizing the amount of content you can put on a disc. Disc-at-once is also best for creating master discs, because disc duplicators can't use discs written with track-at-once. Again, Roxio automates this process; Nero picks it for you, but also allows you to change the option if you choose.
