An ISO represents an optical-disc file system. A USB drive may contain partitions, an EFI system partition, and boot sectors that an ISO file does not preserve. If you need an exact copy of a bootable USB, use a raw whole-device image; if you only need its files, copy them or make a file backup. Renaming an image to .iso does not make it bootable.
Step 1. In Disk Management, identify the USB drive by model and size. Check whether it has one data volume or multiple partitions. Do not select the Windows system disk by mistake.
Step 2. If you only need documents, copy them to another drive and open a sample. If you need all partitions and boot information, choose a trustworthy whole-device imaging tool that produces a raw image, commonly .img or .bin.
Step 3. If the USB was originally created from a Windows installation ISO, the simplest reliable route is to obtain the official ISO again and recreate the installation USB. Do not assume that reading files from the USB reconstructs the original ISO exactly.
Step 1. On Windows, install a reputable USB imaging utility from its publisher. Connect only the intended source USB if possible. In the utility select Read or Create image from device, not Write.
Step 2. Select the USB device by its capacity and letter. Choose an image path on a separate disk with free space at least as large as the USB's full capacity, then start reading. A raw image includes unused space and can be large.
Step 3. When reading completes, record the file size and verify the utility's checksum if it offers one. To restore, select the image as source and a separate target USB. Check the target twice: writing the image overwrites its partitions.
A raw image of a 64 GB USB drive can occupy roughly 64 GB even when only a few GB of files are visible. Some imaging tools compress empty blocks, but the restore target may still need to be at least as large as the original drive in sectors, not just the same advertised capacity.
If the source USB simply holds files for an optical-disc-compatible installer, an ISO-authoring tool may build a new ISO from those files. Bootability requires the correct boot image and file-system settings; copying files into an ISO is insufficient. Test the ISO in a virtual machine before distributing it.
For personal data, a ZIP archive or file backup is usually easier to browse than an ISO. For a factory recovery USB, keep the original media or a full raw image, because hidden partitions and vendor boot information may be essential. Keep the original untouched until the replacement USB has been tested.
Qiling Disk Master can protect files or disks, but its backup image is not an ISO. Use it for restoration through Qiling, not as a file to mount as Windows installation media. Keep an independently verified copy of important USB files before recreating boot media.