OK I'll try to explain this as best I can Since the first time Ive posted Ive managed to get a plugin pack installed. This was Vandermottens. I have also figured out a way to get most of the plugins onto Paint.net but its a very roundabout way (I'll explain that later on). The plugins so far that have not gone into Paint.net are Boltbaits pack, Pyrochilds pack, dpyplugins 5.1, the Alpha mask plugin and the align object plugin. Some of the plugins (ie. the ones other than Vandermottens) say theyre compressed files but Ive unblocked them. Vandermottens was never compressed :S It looks like this:
Now I'll explain how I can get most of the plugins onto paint.net.
I do what was described in the OP. I go into each plugin/pack so they dont show as compressed anymore and then move them into the Effects file again. Paint.net is still not open. It then asked me if I want to copy and replace the original. While that window is open I open paint.net and then click that I want to copy and replace. It then says it doesnt work and to close Paint.net so I do. Then I try again and they go into it. This takes a lot of time since you have to do it individually with each plugin in a pack. It also doesnt work with some plugins (cant remember which ones).
Maybe theres no fix for this LOL. Or maybe Ive just done everything completely wrong LOL