"You can only import binary registry files from within the registry editor."

What editor are you using? That looks like a legitimate reg file, but if you saved it in something other than Notepad you might have inadvertently added extra formatting codes.

I was having this problem as well - I had read to make sure it started with Windows Registry Editor Version 5.00 and that it was saved in ASCII or UTF-16 LE (Little Endian), but was still getting the error.

As it was though, I had a blank line before the 'Windows Registry' header - so I tried deleting that and it worked.