Installer deletes existing directory after failure during install (running elevated).

Currently, when the user selects a read-only directory for installation, he/she is prompted with a question if he/she wants the installer to use elevated permissions and then continues installation, if the user chooses yes. However the installation fails, if the elevated permissions are not enough and the target directory is deleted, after the installation ends.
I suggest, the user can not select a folder, that is write-protected for installation.