Instead of using Windows format:
Windows Explorer often caches the USB drive even after you think it has been released. Rufus tries to lock the device for exclusive access, but Explorer denies it. rufus access to device denied windows 7
Sometimes, Windows might still have a lock on the device. Instead of using Windows format: Windows Explorer often
Windows 7’s generic USB driver ( usbstor.sys ) can become corrupted. but Explorer denies it. Sometimes
If DiskPart is also giving errors, the volume is likely mounted in a way that prevents raw writes. Force-unmount it:
If you want, tell me which USB model and the exact Rufus version and I’ll suggest the most likely next step.