I found winlogon.exe was using over 800MB of memory on my Unity 5.0(1) server. OS is 2003 SP1.
Per google-research, this is caused by KB912354.
We were also getting Application Event Log errors with Windows Product Activation every minute.
Temp fix per some internet sources is to RDP to console. This lead to a full Unity outage due to KB928046
Tonight we will apply Server Updates Wizard for Unity (2.0(12)), but this does NOT list the winlogon.exe memory leak.
How do we patch Unity 5.0(1), Windows 2003 SP1 for KB912354