Could be the download manager it's referring to.
Go to ftp://ftp.adobe.com/pub/adobe/reader/win/10.x/10.1.0/ and download/install AdbeRdr1010_en_US.exe to see if that works. This will skip the download manager.
Yes, I tried avoiding download manager
a number of ways. Your link worked. Thank you!
Thanks so much! This link worked for me also. I struggled for two days trying to reinstall Adobe Reader. I tried to eradicate ALL traces of Adobe products on my system, even manually clearing registry keys. None of it worked - the download manager still continued to report "Application is already installed"