This behavior annoys me quite a lot. I specified '....\bin\Debug\' as output folder for all projects.
When opening a solution, VS creates an empty bin/debug (or /release when in release mode) folder in the parent directory or even the parent of the parent directory of the actual bin folder specified in the project files. After deleting these useless folders, they are not recreated even on a full rebuild.
I'm not sure why VS acts like this. Is this a bug or is there a mistake in my configuration? If you need more information, I'd be glad to add.