Windows.old present after clean install

Turns out I was ratted -_-. Followed the clean install I think correctly but yet there is still a windows.old folder I had some sort of rat/ info stealer on my old os so I clean installed yet the windows.old folder is there. As seen below there is another device there but that not my internal drive is it? Is that not the usb media drive? Was I supposed to delete it too cause the tutorial said not to. This may be irrelevant I read in the tutorial that it was subject to change but the second image window did not pop up so I didn’t get to click custom just went straight to third window

windowsforum.net