Have to tried to disable first the McAfee Access protection, if not than try it.
Moved to ePO
Are you on 64-bit Windows? If so, the location is HKLM\SOFTWARE\Wow6432Node\Network Associates\ePolicy Orchestrator\Agent
What are you actually trying to do, though? The data in that registry value does not control how the agent finds the server - that is governed by the sitelist.