Go to the location of your project that's giving you this error and select the folder, then right click it and press "Delete". Once that is done go to your Recycle Bin and delete the object permanently. After that go into the C++ start page and try to open up your project. If it give you an error, close the error message and you should be all good.
You cant Run the .DLL into a Process without a Injector so it brings you an error that it cant be debugged, so the only way to test your hack is to Inject it into a game thats the only way to get the .DLL working. It worked for me (: