That's the telltale sign of a tryout version of a third-party plugin. To get rid of it, pay for it and get a registration code. If you already paid, contact the people sho sold it to you.
I will repeat what Dave said and what has been said hundreds of times on this and other forums. If there's a Red Cross or other watermark on your project then you have a plug-in that is not been paid for or registered That's all it is to it.
In this case, it appears that Trapcode Particular is the unregistered plugin.