I think you have installed the "functional content." This provides a few menus, no buttons etc.
From the disk install (I did not know it was there), and based on a comment on the first link above, it may not be up to date. You can always delete those folders and start over. I would move on to step 2: installing the complete library.
The files uou need are the ones that you cannot unzip. This appears to happen when the download is not correct. I have seen this most often with Mac users; they benefitted fronm using a download manager to get the correct file.
Re: EncoreContent English.zip (1.1GB)...
Mine is 1.Gig.