The location which GetMem mentions is usually not used for a secondary installation. Find the file lazarus.cfg in the Lazarus installation folder, open it, and get the profile folder from there. Or, open the properties of the link which starts Lazarus; if there is a parameter -pcp or --primary-config-path then the associated string is the path to the profile.
Another issue comes to my mind why Lazarus persistently does not use the correct fpc: Did you add fpc to the Windows path? Open a cmd windows and type "path" to see the current path settings. If there is anything related to fpc or Lazarus remove it. Dont't pollute the Windows path with these programs, you call for trouble if you have multiple installations.