I put some in the addon scenery folder, some in the main scenery folder, others in the world scenery and texture folders, I just followed the instructions and dont remember what they were, in order to go and fish them out and delete them.As you say, I'm robably stuck with the problem. Jack.
OK, now we can help you by what your telling us above.
When ever you are going to add scenery or textures that are going to over write your originials in the main scenery/texture folders, you have to (should) always make copys of the originals ( make a folder somewhere in your My Documents or wherever you like to put your ORGs), so if the 3rd party stuff don't work, than you'll always be able to put back the ORGs. So like I said in my other post, when you fire up the sim and you get the pop-ups, just write down the name of the file, than you can do a search to find them, delete them, and than you can use the repair option to replace the originals, or if you have to the dreaded reinstall

P.S. if you down load an add-on with an auto installer (I personally) don't let it install anything into the main FSX folders. I install the files to a folder I'll create, so I can see whats in the add-on, and then I will (make my back-ups first) than install the files myself. Also, I have a small compostion notebook that I write down what went were, so if something doesn't work, I can fix it pronto! Hope this helps you, good luck, and welcome to the V!