What the title says, happened to a friend. While trying to transfer some files to his usb stick, a notification popped up, which he couldn't close, so he restarted his machine. After restart, his was prompted with the try ubuntu, which is automatically selected or install ubuntu. I asked him what the notification said, to which he told me he didn't pay attention to, but it had the word net. Any ideas to what happened?
Edit: Problem solved, friend is stupid. The usb he used had Ubuntu installation files. Thanks for the tips!