I made a Parallels Desktop image of my WinXP setup that's 5.29 GB. I figured that would fit on a single (Mac only) data DVD with compression, so I chose "save as disc image" to find out. Sure enough, the disc image is well under 4GB (so much smaller I considered installing other stuff in the image first, but decided against it.)
I tried to burn the image, and I get the message:
There's not enough free space on this disc: 2774147 sectors (5.29 GB) are needed, 2298496 sectors (4.38 GB) are available.
I figured perhaps it was doing something stupid like trying to burn the disc uncompressed. So I tried it all over, without saving as a disc image. I get the same message, even though the "compressed" checkbox is checked. If I check the compressed checkbox, and the CONTENTS are 5.29 GB, it's obviously IGNORING the compression option and preventing me from burning. Similarly, the stupid software won't even burn an image that's well under 4GB because it interprets its contents as being larger than the disc.
I'm just about ready to give up on this software. Every new version comes with a nasty surprise.
Incidentally, I just tried it with 7.1 and I get the same thing. WTF!? I burned one before and it worked. I also just did a new "save as disc image" to find out what the exact file size of the image (as reported by the finder is.) It is 3.05 GB. Toast is obviously capable of compressing it and putting it on a disc--it's just being obstinate (or rather, buggy.)