Dear Community
Just wanted to share something which I hope helps others.
I have today been trying to install SEP 12.1.2015.2015 (RU2) on a shiny new Lenovo Tablet 2 - running Windows 8 Professional 32bit.
I have been unable to install it - the installer would get as far as saying "0 seconds remaining" - then hang for a little while then disappear.
When checking the SEP_INST.log file in appdata\local\temp - it was reporting error 1603
The solution was to
1. Turn off Windows defender
2. Remove windows update: KB2781197 then reboot (reboot took about 10 mins while stuck on configuring windows updates screen)
3. once rebooted - confirm the patch is removed one last time
4. Install SEP12.1 RU2 again.
This now allowed me to install the SEP client.
Really hope this helps someone else, I wasted the entire day on this!