I have 2 instances of SDP, each running on Win Server 2012 R2 VMs, in different data centers. I updated the running NS2 instance from 1.15 to .16, no problem. Changed to the NS1 system, the upgrade failed, repeatedly, with the error, (1001?), 'the service is marked for deletion'. Each time, SDP rolled back the install, but the SDP GUI was no longer visible. What I did to fix this is to find the sdnsplus service in Task Manager, right-click on the service, choose 'Go to details', then killed the sdsmain.exe process in the Details tab view of Task Manager. Once this core engine process was down, I installed the 1.16 executable, chose a 'Complete' install, and then the NS1 instance reappeared, with my zones intact. Now I'm a happy camper!