Finally offered 1709

I have 2 similar PCs. Both are running 3.4 GHz Intel i5 processors
and have 16 GB of RAM installed. Both have SSDs for the system drive.
One has plentry of space left (hundreds of GB) while the other only my
main PC) has about 50 GB free. I was finally offered the update to
1709 today, but I may have caused it. I was on the page that said my
pc is up-to-date, but pressed check for updates anyway. It came back
with 1709 being available. I told it to go ahead and it downloaded it
in about 7 minutes (50 mb/sec connection). It then went to "preparing
for update" for what seemed like a long time (30 minutes?). It then
said it couldn't continue because an incompatible program was
installed - PGP desktop. I uninstalled PGP and started over. The
download was quicker this time (I assume it already had a bunch of it
from the first attempt.) But, "preparing for update" took even
longer. It eventually completed with 1709 installed and working.

That was my backup pc. Then, I decided to update my main pc. I went
to the update page where it said I was already up-to-date. Pressing
check for updates displayed 1709 as being available. This time, I
uninstalled PGP desktop first like I should have done on the other
one. It went through download, preparing to update, and then went
back to the "your pc is up-to-date" page. No error messages of any
kind were displayed. If I was a non-technical user, I would have
assumed the update had completed. Knowing better, I once again
clicked check for updates and, once again, was offered 1709. It once
again went through download, preparing, etc, and finally completed the
update. Total time spent = 3 hours. I hate the way things fail with
no error messages. Anyway, both my PCs are now running 1709 with no
issues.

I ask this everytime I upgrade to a new version of Windows 10 - Does
anyone know why I have to uninstall PGP desktop in order to do the
upgrade? I know it is an old program, but it works well for me and
reinstalls just fine after a major upgrade. Does it do something odd
in the way it operates or is it just on some Microsoft list of
incompatible programs?