Hi Malcom,
I also use Internet Download Manager to download the file in its zipped form. For me, Internet Download Manager does not unzip the file. Are you then unzipping with a separate piece of software or do you have some setting in Internet Download Manager turned on that also unzips. Donwload and unzip should be maintained as two separate processes for the very reason that caused you a problem. 7Zip is the best unzipper. It's standard extraction retains the parent folder which is the proper unzipping methodology otherwise you could find files all over your desktop and lose the parent folder. In addition, 7Zip is able to handle very large files where the Windows 7 unzip sometimes has a problem. If you use the default Windows 7 extraction, you need to make sure you are choosing the extraction choice that maintains the parent folder.
Many other RTMM sceneries will need retention of the parent folder since you cannot count on a second parent folder for the installable Scenery inside the first.
Rod
Rod