I'm trying to turn off several of the processes that load whenever I startup my iMac. I looked in the Activity Monitor and it shows several different processes that I don't need taking up memory. I quit each process and when I restart they just come back.

So I checked the Startup Items in System Preferences to see if I can remove them from there, but none of them are listed. Why wouldn't the processes that show in the Activity Monitor match the ones set to launch in the Startup Items? Is there another place that I can go to stop these from loading when I start my computer?