DO NOT BURN AN IMAGE from the ISO file. You can use a DVD but you have to burn the ISO file itself onto the disc, not the image that it generates. This is 100% backward from what is stated in the OS administration guide.
There is no 6.x to 6.x upgrade kit available--the only available kits are 4.x/5.x to 6.x. DVDs ordered from Cisco WILL NOT WORK for upgrades from 6.x versions because they contain the files themselves and not an ISO. You must download the files, concatenate them and either burn the ISO file itself to a DVD (in "mastering" mode for Vista sufferers) or put it on an SFTP server.
The release notes contain no instructions beyond concatenating the downloaded file, and the OS administration guide says the exact opposite of what is true: "...you must create an ISO image on a writable DVD from the upgrade file..." Only the remote source upgrade section alludes to the .sgn.iso file. With regard to a DVD/CD upgrade, the guide is COMPLETELY WRONG and the release notes are silent, so please save your admonition to RTFM.
