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How to install Windows 10 from USB (Without CD, Only ISO)

Installation Right From Usb Drive.png In this guide we’ll take a closer look at installing Windows 10 from your USB stick (pen drive) and what utilities can help you to get this done e.g. to verify that your drive is actually bootable.

Creating a bootable USB drive to install Windows 10 from USB takes inexperienced users approx. 30 minutes to 1 hour. Please note that many regular USB sticks are not bootable and you may need a proper flash drive with boot-support.

StepWhat are we doing?
1Download Windows 10 ISO
2Mounting Windows 10 ISO
3Formatting USB Drive (NTFS)
4Opening Elevated Command Prompt
5Creating Primary Partition
6Making USB Drive Bootable
7Copying Windows 10 To USB
8Booting Directly From USB (UEFI)

If you run into any issues, try our troubleshooting tips:

Step
1Troubleshooting: Is The USB Drive Bootable?
2Troubleshooting: Access Denied: The Update May Be Unreliable
3Troubleshooting: Access Denied: Could Not Map Drive Partitions

Step 1: Download Windows 10 ISO (32-bit or 64-bit)

Please note: You need to be on a 64-bit OS to be able to create a 64-bit bootable Windows 10 drive.

Before we can install Windows 10 via our USB device, we obviously need the ISO file, which you can download here:

You also need to free at least 5GB of disk space for the bootable USB.

Step 2: Mounting Windows 10 ISO

6. Step Next, we are going to mount the ISO file. Luckily, Windows has built-in support for mounting ISO’s.

Mounting Windows 10 Iso.png

7. Step Check what letter Windows is assigning to the mounted Windows 10 disc:

Mounted Windows 10 Iso File.png

Step 3: Formatting Your USB Drive

Before we can install Windows 10 we need to copy the data from the ISO to our drive, but that won’t work if it doesn’t have an active boot partition, so we need to format the drive first.

1. Step Hit Windows key + R to open Run and copy and paste this command diskmgmt.msc:

Open Disk Management Panel On Windows.png

2. Step This will open the disk management panel

3. Step Select your USB pen drive e.g. KINGSTON (L:). It should be the last disk of the list. Make sure it’s really your USB drive, because we are going to format it now (erase all data). You can verify that by opening the Windows explorer and opening the drive with the exact same letter. Move any files you still need from the USB drive to a safe location:

Formatting Kingston Usb Pen Drive.png

4. Step The option “Perform a quick format” should be enabled and the filesystem should be changed from FAT32 to NTFS. You can keep the allocation unit size.

5. Step You will be given one last warning that this will erase all data, confirm AFTER double-checking that nothing you need is on it. Even if it appears empty on first glance, certain files like log files or documents don’t take a lot of disk space and are often missed. So better safe than sorry and check it again, then proceed.

Formatting This Volume Will Erase All Data.png

Now open the Windows explorer. The icon of your USB drive might or might not change at this point. The mounted ISO file and the USB drive may at some point have the same icons.

New Ntfs Volume.png

Step 4: Opening Elevated Command Prompt

8. Step Open an elevated command prompt. If you’re on Windows 8, right-click on the Start button and you will see the poweruser menu. Use the option Command Prompt (Admin)

Opening Elevated Command Prompt On Windows 8.Png

9. Step Alrighty, we are now ready to make our USB drive bootable!

Step 5: Creating Primary Partition On Our USB Drive (IMPORTANT!)

**Before proceeding verify the disk number of the USB device you want to install Windows 10 with! Selecting the incorrect disk will prevent this from working**

  • Enter DISKPART
  • Enter LIST DISK to verify the disk number of your USB drive again (as a pre-caution)
  • Enter SELECT DISK 5

Important: Verify in the disk manager that your USB drive is disk 5, replace 5 if necessary

Create Bootable Partition On Usb.png

  • Enter SELECT PARTITION 1
  • Enter ACTIVE

You should get responses that say partition 1 is now the selected partition and then DiskPart marked the current partition as active.

Finally enter EXIT to close the prompt. Next we are use the command bootsect to change the volume bootcode or your PC wouldn’t recognize the Windows 10 installer.

Step 6: Making USB Bootable via BOOTSECT.exe

Open an elevated command prompt again.

The command BOOTSECT.EXE /NT60 L: can make a target volume compatible with bootcode and will be recognized by your BIOS as a bootable drive. Replace L: with the letter Windows assigned to your USB drive (not the one we just mounted).

Making Usb Drive Bootable.png

You should get a success message that states that the bootcode was updated on your USB drive. You should also see a volume code.

NOTE: Before you proceed with the next stop (copying the content) you may want to verify that the drive is now bootable first. Because if you copy the files over and it’s not bootable, you will have to copy the files again.

Step 7: Copy Windows 10 ISO Content To Bootable USB Drive

The last step is easy, in order to install Windows 10 from USB just copy the entire content of the mounted drive onto your USB drive. This works, nothing else is required to make the installer work.

Copy Iso Content To Bootable Usb Pen Drive.png

It will take approx. 10 minutes depending on the write speed of your USB drive.

How Long Does It Take To Create Bootable Usb.png

KINGSTON drives are really fast and it copied the files quite fast onto the drive.

When you’re done, unplug the drive (eject first via tray) and plug it into your laptop or 2nd PC to install Windows 10

You’re good to go, have fun with Windows 10 and keep testing!

Step 8: Entering BIOS / Changing Boot Order / Boot From USB Directly

Unfortunately, UEFI is a mess and makes beginners spin their heads around. All laptop manufacturers use different key combos for the boot or BIOS menu. Sometimes you even have to open the advanced startup options to boot directly into the UEFI BIOS.

Boot From Usb
Picture: ASUS Laptop, Hold CTRL And Keep Hitting ESC to open boot manager that allows you to boot directly from any plugged in USB drives.

We have an extensive guide on the UEFI BIOS and how to disable secure boot that will help you to change the boot order.

Once you are able to either open the direct boot popup or go into the BIOS to change boot order, you are good to go. Post a comment if you need additional help with this.

Troubleshooting: Not usable free extent could be found

It’s possible that you will run the following error:

No usable free extent could be found. It may be that there is insufficient free space to create a partition.

This may happen when a partition already exists and you forgot to correctly format the drive or issue the command CLEAN via diskpart.

Is USB Drive Bootable? (Verify Without Restart)

Ok, the first thing we are going to try is to see if the USB drive is bootable.

Download the file MovaLiveUSB.zip and extract it right on your USB drive (not your actual drive!!) This tool by mobatek.net is a great way to quickly verify that you can actually boot from the device without having to restart each time.

After extracting it run it (right-click Run as Administrator). The tool will verify if the drive is bootable all by itself. You may have to confirm a question in french with Qui (Yes).

If the drive is bootable and there are no files on it yet it should say “An operating system wasn’t found. Try disconnecting any drives that don’t contain an operating system. If you have already copied Windows 10 onto the drive, it will actually boot from the CD without you having to restart.

Verify Usb Drive Is Bootable.png

If the drive is not bootable you will get an error “BOOT FAILURE” (INT18 ERROR).

Kingston Data Traveler G3: No Boot Support

Not all USB sticks and drives support USB boot. Kingston Data Traveler may be one of them. Please try another USB device if you have any to avoid troubleshooting.

There are other USB drives that you cannot use for this guide. You may have to acquire another USB drive before you can install Windows 10 from USB.

Access Denied: Could Not Map Drive Partitions

If you get the error “Could Not Map Drive Partitions” you forgot to start your command prompt with elevated rights (see above)

Could Not Map Drive Access Denied.png

Once you start an elevated command prompt that error will disappear.

Access Denied: The update may be unreliable since the volume could not be locked during the update

When you get that error, Windows will most likely fail to make your pen drive bootable. It will most likely also say:

Access is denied.

How to fix that? It is entirely possibly that some process is accessing the USB drive. Make sure to close all programs running in the background and do not actually open the drive itself (double-click on drive within explorer) to copy the content of the Windows 10 ISO.

Finally, you can go ahead and install Windows 10

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Published: Wednesday, March 25th, 2015 Last Modified: April 5, 2016

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