Just a note to any users out there who are considering double layer (DL) DVD+R disks for archiving -- the "Memorex" brand of these disks is SUBSTANDARD and ERROR-PRONE. I have had to discard all such disks that I purchased due to burning errors. I have used Nero's CD-DVD Speed utility to gauge the quality of these disks, and it confirms that they are bad to poor.
The web site digitalFAQ.com has an online guide that discusses the quality of various DVD brands, and especially the difference between the BRAND and the actual manufacturer of the media (http://www.digitalfaq.com/media/index.htm).
After reading the above guide, I have switched to Verbatim disks, and altough not error-free, have given me MUCH better results.