The OPC Server can be configured for being used as a service. Go to Start | Run and type "regedit"

In the Registry Editor, follow the tree to the following location:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run

Once in the registry at the above location,

right click on RUN and choose New | String Value.
Now highlight the new string and right click Modify.
In the pop up window, add the path to the BACnet OPC Server file

Once the above changes are made, the OPC Server will automatically start every time the PC boots up.