Out of the box the VMware VirtualCenter Server Service (vpxd aka c# client users) is delayed for 120 seconds in Windows. I am running Windows 2012 R2 and vCenter 5.5 u2/u3. The goal is to lower the start time of the service after an OS reboot.
add a new DWORD (32-bit) with a Value Name: AutoStartDelay Value date = 45
45 seconds is just enough time to allow all of the automatic windows services to start; you can experiment with lower numbers.
Side note- HKEY_LOCAL_MACHINESYSTEMCurrentControlSetControl Adding AutoStartDelay applies for ALL delayed services; we just want the single delayed service.