# OptiPlex 790 Windows 10 clean reinstall with USB flash



## chueh (Sep 27, 2008)

I searched online tutorials to find similar boot menu and bios setup to mine, but I cannot. Thus, I am very confused how to CLEAN INSTALL my window 10, for my computer boots regularly even with the USB Storage as the top priority to boot.

Boot Menu on mine:









Legacy Boot:
OnBoard INC
PO: ST......
CD/DVD...

Other Options:
BIOS Setup
Dianostic
Intel

I *CHOSE BIOS Setup *

Then,









The right panel contains 2 parts: *boot sequence* at the top and* boot option* at bottom.

I switch the order for the boot sequence to be: 1. *USB Storage *2. OnBoard 3. etc...

The LEGACY is checked under boot option. When I clicked the UEFI, the boot sequence is all disabled. Thus, I assume that I would leave LEGACY checked as it is.

Then, I saved and exit, and reboot.

After the reboot, computer went through regular boot and went to the desktop screen, without booting with the USB........

What steps did I miss?

Thanks


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## TerryNet (Mar 23, 2005)

chueh said:


> What steps did I miss?


Making sure that the USB media is bootable? Testing it on another computer may help.


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## Couriant (Mar 26, 2002)

according to your second picture, your HDD is priority over the USB.

You don't really need to have the USB as priority. The issue I think you are having is that the USB stick you have for the clean install is set to UEFI but your computer seems to be only doing Legacy, or the USB drive is not being recognized.

Try using UEFI, then apply and exit. Also, try a different USB port. If it doesn't work, then Terry's idea of the USB not being bootable is probably the issue.

What is the service tag of the computer? You can find that under System Information in the BIOS.


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## managed (May 24, 2003)

In the Bios at the 2nd picture click on USB Storage Device _on the right_ to highlight it then click on the up arrow to move it to the top, Save and Exit.

The section on the left with the ticks only means a ticked device is in the list, not it's position within the list.

The Usb device should have appeared in the 1st picture but did not so you may have to change to UEFI mode.

Exactly how did you make the Usb stick ?


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## chueh (Sep 27, 2008)

1. Sorry about posting the wrong 2nd picture. I actually made USB to the very top yet didn't post the picture here.

I actually did save Windows 10 directly to USB flash from the Installations Media, as well as Only Save As ISO File onto my desktop, and then manually mount it with a virtual DVD by performing elevated CMD for disport.
The USB Flash should be bootable, but it doesn't work so.

2. When I clicked on UEFI, then all the boot sequence disappeared. Is it normal? I was afraid to choose UEFI, for everything at the top boot items were all in grey.

3. Aside from the above issues, no matter if I changed the boot sequence or directly clicked on SETUP.EXE after MOUNTING windows.iso without using the USB or DVD, it NEVER shows up the picture below as all the tutorials online at all (Mine always starts with INSTALLING WINDOWS "Your PC will restart several times...This will take a while," with light blue screen color directly, NOT the following screenshots with Deep blue screen color for WINDOWS SETUP below)









Or this:









I have attempted to DELETE partitions, yet this screen never shows up on mine, so I can never delete partitions to make CLEAN INSTALL


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## managed (May 24, 2003)

I would start again and make the Usb stick using the Media Creation Tool :- https://www.microsoft.com/en-gb/sof...s10?d2784474-fdb0-4e9d-9e47-5e88c0e053ec=True

The resulting Usb stick will boot if the computer uses a legacy or UEFI bios.


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## Couriant (Mar 26, 2002)

With an ISO you need to use Rufus to create the USB stick. But the media creation tool will work too


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## chueh (Sep 27, 2008)

Thank you


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## Couriant (Mar 26, 2002)

chueh said:


> 1. Sorry about posting the wrong 2nd picture. I actually made USB to the very top yet didn't post the picture here.
> 
> I actually did save Windows 10 directly to USB flash from the Installations Media, as well as Only Save As ISO File onto my desktop, and then manually mount it with a virtual DVD by performing elevated CMD for disport.
> The USB Flash should be bootable, but it doesn't work so.
> ...


*To confirm your information here:

1: You cannot run the setup from your desktop and do a clean install. You need to use a tool like Rufus to extract and create a bootable USB (recommended) or maybe DVD. The Media Creation Tool that was mentioned does the same thing, but should be more updated than some Windows ISOs.

2: Yes, that is normal because you are changing the type of boot. You can always revert back. UEFI is the standard now that has other security options like Secure Boot.

3: That may be due to the ISO that you are using, or that you are running it from your desktop.

Note, I have found that Dell's can be picky on the USB port that you use to install Windows.*


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## chueh (Sep 27, 2008)

Couriant said:


> *To confirm your information here:
> 
> 1: You cannot run the setup from your desktop and do a clean install. You need to use a tool like Rufus to extract and create a bootable USB (recommended) or maybe DVD. The Media Creation Tool that was mentioned does the same thing, but should be more updated than some Windows ISOs.
> 
> ...


Thank you for your answers Couriant.

Although I still couldn't run a CLEAN INSTALL, at least now my computer is working like normal.

Thank you everybody for your response


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