John Galt said:
No way. I've burned over 150 DVDs+R discs and have not had to format
a single one. Not one.
If you want to use UDF format (though why you'd do this with a
non-rewriteable disc is questionable) Windows will want to "format" it
regardless of whether it's rewriteable or not. A UDF format disc can be
treated as though it were a giant floppy (or tiny hard drive), the only
difference being that deleting files on a non-rewriteable disc will not
actually reclaim any space.
If you're burning a disc that will play in a DVD player (for example,
movies) then neither type of disc (rewriteable or write-once) requires
formatting. They're either burned in one session and automatically
finalised or they're burned in multiple sessions and will probably require
finalising to guarantee a DVD player will be able to read them. The
difference here is that rewriteable discs can be erased, non-rewriteable
discs can not.
What the original poster was getting at was: when you insert a brand new
blank disc into the drive, Windows detects this and asks you which type of
file system you want to use: ISO or UDF. Windows calls them "Mastered" or
"Live File System" respectively.
Unfortunately, after all that, I don't know the answer to why it's no longer
doing this, unless it's in the Autoplay settings somewhere. I've found +R
discs to be somewhat unreliable in my machine and try to use -R (or -R/W for
UDF) by preference.