Alert! Package folder already used in project

Hello, I created a project with existing sources. I removed after that project. And now I am trying to create a new project with the same sources used by the first, but this message appears:
'Package folder already used in project....' (with the name of the first project).

I looked at my computer and there is no trace of the old project. Does anyone know how I can resolve this? I have tried everything and nothing works.

Thanks in advance. Raquel