I had 365 installed on my Lenovo ThinkStation as part of a mirror transfer from a failing laptop. I was unhappy with the Outlook configuration and it looked like the easiest fix would be to uninstall and reinstall 365. The uninstall worked fine. I then downloaded the 365 installer, which only took half a minute or so, but when it started to run, the installer window started to replicate itself every few seconds. The only way to stop it is to restart. I tried it a couple of times, same thing; I tried deleting the downloaded file (and removing it from the recycle bin) and doing it again, same thing, so it's not a corrupted install file. I am using Norton antivirus, turned off during this operation.