Extras folder
If you want to burn DVD-ROM content to your disc, type the path to the folder that contains the files you want to include (or select the box and click the Browse button to choose a folder).
When you choose a folder, all files within that folder will be written to the root of your DVD. If you want to place the content in a subfolder at the root of the DVD, create a subfolder within your specified extras folder:
• For example, if c:\media\extras\ is your extras folder, all files within c:\extras will be written to the root of the DVD.
• For example, if c:\media\extras\ is your extras folder, you could place the files you want to burn in a c:\media\extras\DVD-ROM subfolder so that DVD-ROM folder and its contents would be written to the root of the DVD..
Click the Change Media button to browse to a folder.
Click the Clear Media button to remove a folder.
I would very much recommend putting it in a folder though. I've seen quite a few DVD players freak out when they see a file in the root folder. Some will report errors, some will refuse to play the disc.
\Extras\ is used so commonly that it's almost a defacto standard. Go with that and put your files in there.
I disagree. If the DVD player freaks out about this then theres likely something else wrong with the way the DVD was constructed. There are lots and lots of major DVD titles that put autorun.inf's and executables at the root - major motion picture studios wouldn't do this if it was a significantly widespread issue with players.
I'd guess that many stand-alone boxes will try to decipher whatever's in the root looking for DivX/Xvid, jpeg, wma etc... It might have something to do with book/disc type set as well. I'd also guess that the autorun.inf file is small enough not to cause concerns.
At any rate I'd suggest Imgburn rather than Nero for both adding the folder with extra content and burning, but that's just my opinion.
According to the early purists, Nero wasn't too exact about obeying all the rules put down in the specs. I've never had problems with Nero, but, Imgburn was designed from the start to stick as exactly to spec as possible, and includes bit setting... General opinion seems to be it's the most accurate and best out there for writing DVDs because of that.
How much of that is fact or fiction I can't say, but I tend to be overcautious, so have used Imgburn for quite some time without a problem.