My computer has two disks: A solid-state disk C: to hold the OS and critical apps, and a larger hard drive D: for my user files and less-critical apps. I had Firefox installed and working. Then I ran into a permissions problem that I can only call cancerous: files I copied over from my old computer (via an external HD) had permissions that didn't allow writing in the directories; I couldn't even delete them when logged in as admin. So I reformatted D: and copied the files again (using a different method). As soon as I had done so, I changed the permissions on D:\ so my non-admin user has "full control" on that disk. I still have a permissions problem but it's less severe. I'll deal with that in due time. (I hope) But I had the Firefox executable stored on D:, so when I reformatted I lost Firefox -- executable and settings. Shouldn't be a problem, right? Just re-install and sync. But I can't get Firefox to install! The installer (Firefox Setup Stub 48.0.1.exe) runs, I give it admin permission. It offers me "Upgrade" as an option. I click that and get a window that says "Downloading Firefox". When it's finished downloading, it exits without an error message, but I still don't have Firefox. Just a shortcut that doesn't work -- refers to a nonexistent file. Hmm... I just looked at the properties on the shortcut, and the "Target" is "C:\Users\barry_2\AppData\Local\Mozilla Firefox\firefox.exe" That can't be right, can it?