Take a look at HKLM\SOFTWARE\Wow6432Node\Network Associates\TVD\Shared Components\Framework\
AgentMode -- 1 is managed, 0 is not managed.
This will be slightly different on a 32-bit machine. This one should be true for 5.x Agents, but on one of my machines with 184.108.40.2060, I don't have this value, so you might check...
HKLM\SOFTWARE\Wow6432Node\Network Associates\ePolicy Orchestrator\Agent\
AgentGUID should only report a value if it is managed already, but you may want to check on an unmanaged 4.8, since I don't have one to check on.