dottie236, could you please right-click on the downloaded file in Windows Explorer, click "properties", and let us know what the "size" of the file is in the window that pops up?
It's possible that they have changed the installer, but my version says 611 MB (641,609,367 bytes).
If your file is much smaller than this, then the download has been aborted. You could try installing a download program like
or [url=http://getright.com/]Getright. It should take over the download from Internet Explorer (or whatever you are using) and it might help.
If your file is the same size, then there is some sort of corruption happening in the download. Perhaps you could enquire with GOG support again, and point them at this thread so they know what you've tried. You might even want to ask your internet provider about the problem.