Reinstalling W10 on a GPT disk from a USB boot disk

Xlrtech · 15 May 2017

I'm working on an HP laptop whose Windows installation has been damaged following the user falling for the Microsoft scam. Having made several attempts at repairing the damage without success, the obvious solution is to reinstall Windows.

And here's the problem: I have a Windows 10 boot disk on a USB stick; in order to get the BIOS to see it, I put the PC into legacy mode, then boot from the stick. On attempting to install on the appropriate partition, I get the message that Windows can't be installed there, as it's a GPT disk.

Since Windows was already installed there, what's the problem? Do I need a special version of the boot disk? A little research seems to suggest that I need to convert the disk to MBR; this seems counter-intuitive, since GPT is the more modern system, and the PC and its damaged Windows 10 installation were running satisfactorily prior to the damage occurring.

Any advice much appreciated.

Samuria · 15 May 2017

Your getting that as you set it to legacy mode. Have you got the latest iso with the latest version of windows no sense putting an old version on

NavyLCDR · 15 May 2017

How did you make the USB flash drive? I'm willing to bet your answer is going to be, "With RUFUS"

Mystere · 15 May 2017

Why are you enabling legacy mode? Have you tried using the boot menu (in UEFI mode)? Usually F12 at boot, you want to select the UEFI boot from USB.

NavyLCDR · 15 May 2017

Mystere said:

Why are you enabling legacy mode? Have you tried using the boot menu (in UEFI mode)? Usually F12 at boot, you want to select the UEFI boot from USB.

The OP posted:

Xlrtech said:

And here's the problem: I have a Windows 10 boot disk on a USB stick; in order to get the BIOS to see it, I put the PC into legacy mode, then boot from the stick.

I suspect the USB flash drive is formatted as NTFS which most computers will not boot from in UEFI mode and that it needs to be created again using FAT32.

cereberus · 15 May 2017

Some older bioses do not boot from usb drives in EUFI mode.

So trick here is to use rufus with downloaded iso and select 'mbr partition scheme for UEFI'

This allows you to boot usb in legacy bios mode BUT installs Windows 10 in UEFI/GPT mode.

After installation, reset bios to UEFI mode.

sygnus21 · 16 May 2017

cereberus said:

Some older bioses do not boot from usb drives in EUFI mode.

I'd be interested to know which chipsets those BIOS's were on because I've not run into a UEFI BIOS (Gigabyte boards) that didn't run a USB drive. I'm going to assume if the BIOS is UEFI, it will run a USB stick. I'm also going to guess the laptop isn't so old that it wouldn't support a USB flash drive.

At any rate I'm with NavyLCDR on it being a format issue. On the other hand it could be a "secure boot" issue where secure boot "may" need to be disabled. I've never had to do this myself in reinstalling or upgrading my system, but some do recommend it be disabled for Windows installs...

The hidden challenges of booting from a USB flash drive

Comp Cmndo · 16 May 2017

For HP, "F9" on power up allows selection of boot device. No changes needed to BIOS.

cereberus · 18 May 2017

sygnus21 said:

I'm going to assume if the BIOS is UEFI, it will run a USB stick.

Never ASSUME anything. If you get it wrong, it can make an ASS of U and Me.

What I stated is true on some older pcs as they did not all implement the UEFI standard properly. I had a Sony where that was the case.

Anyway, if OP uses Rufus and selects "mbr partition for UEFI install", that works on any UEFI pc that can legacy boot as well.

sygnus21 · 18 May 2017

cereberus said:

Never ASSUME anything. If you get it wrong, it can make an ASS of U and Me.

What I stated is true on some older pcs as they did not all implement the UEFI standard properly. I had a Sony where that was the case.

Given your statement, I'd ask what "older pcs" didn't implement UEFI properly? Perhaps a definitive answer would help the OP, seeing they may have such a PC?

Oh, and If you're going to caution me on assuming, than I'm going to caution you on guesswork as fact.

Peace