```uv_fs_rename``` on POSIX systems use ```rename``` and will work only in the bounds of one filesystem. On Windows it uses ```MoveFileExW``` and MSDN says that "When moving a file, the destination can be on a different file system or volume. If the destination is on another drive, you must set the MOVEFILE_COPY_ALLOWED flag in dwFlags.". libuv does not set this flag.