Convert GPT/UEFI to MBR/Legacy

[DnFx91]

Thinking about upgrading my workmate's PC, but that also requires a downgrade to some extent, the replacement machine has way more horsepower but lacks the ability to boot UEFI, and i want just stick his current UEFI boot drive in there to avoid reinstalling our very complicated and fragile Work PC installations. 

 

I read recently that there is now a tool included with windows 10 to convert MBR to GPT, but i want to know if theres a way to do the reverse ?? 

 

So i can convert his current UEFI OS into a Legacy one, and then boot it on the new (older) machine ?

[agent_x007]

1) Use Clover/DUET for (U)EFI/GPT booting
2) GPT to MBR requires full format

[DnFx91]

Just now, agent_x007 said:

1) Use Clover for (U)EFI booting
2) GPT to MBR requires full format

that did occur to me as an option, so i can use clover to boot EFI on a legacy machine ? it's not a hardware limitation then ? I am familiar with clover but i thought that had to be booted as UEFI itself right ?

[GoodBytes]

2 minutes ago, DnFx91 said:

Thinking about upgrading my workmate's PC, but that also requires a downgrade to some extent, the replacement machine has way more horsepower but lacks the ability to boot UEFI, and i want just stick his current UEFI boot drive in there to avoid reinstalling our very complicated and fragile Work PC installations. 

 

I read recently that there is now a tool included with windows 10 to convert MBR to GPT, but i want to know if theres a way to do the reverse ?? 

 

So i can convert his current UEFI OS into a Legacy one, and then boot it on the new (older) machine ?

There is no way to convert back down from GPT to MBR. Microsoft made the tool to go one way only (which actually makes sense in most cases)

[Droidbot]

MBR to GPT works

GPT to MBR doesn't

[DnFx91]

Just now, GoodBytes said:

There is no way to convert back down from GPT to MBR. Microsoft made the tool to go one way only (which actually makes sense in most cases)

hmm bugger, so will clover work ?

[agent_x007]

3 minutes ago, DnFx91 said:

that did occur to me as an option, so i can use clover to boot EFI on a legacy machine ? it's not a hardware limitation then ? I am familiar with clover but i thought that had to be booted as UEFI itself right ?

Clover is 3-rd party EFI booting
I use it to boot from NVMe on PGA 478.

[GoodBytes]

1 minute ago, DnFx91 said:

hmm bugger, so will clover work ?

No idea, personally. Never tried.

[DnFx91]

Just now, agent_x007 said:

Clover is 3-rd party EFI booting

ah makes sense now, just seen the word emulation, i had it in my head that UEFI booting required a physical thing on the motherboard that older PC's don't have. so, lemme get this straight. i clone his entire GPT drive from his current machine, pop it into the replacement machine, go in with partedmagic and configure the clover bootloader in the EFI partition, then reboot and ittl dump me at clover with windows as a bootable option ? 

[agent_x007]

Don't know if you forgot, but Clover requires a Legacy bootable drive to work (you have to select it as boot option in MB's BIOS). It can be a Pendrive/SD Card/HDD/SSD/M.2 SATA, it doesn't matter.
It must be visible as boot option in BIOS.

Keep in mind, that even if Clover is set, cloned Windows may not like new machine's hardware setup (since it has drivers from old one already loaded).

If you set clover correctly it should have option to boot from "EFI"/"Microsoft EFI" (if OS is installed on GPT drive).

[DnFx91]

im now very confused, i tested it anyway with a generic UEFI image, and it booted ???

 

whats going on here, im sure this board doesnt support UEFI

 

It's a supermicro X8DAi

[agent_x007]

Interesting...
I assume, you don't have (U)EFI option in boot menu ?

Try Windows 10 x64 pendrive formatted for EFI booting (ISO image + Rufus 2.16).

[DnFx91]

33 minutes ago, agent_x007 said:

Interesting...
I assume, you don't have (U)EFI option in boot menu ?

Try Windows 10 x64 pendrive formatted for EFI booting (ISO image + Rufus 2.16).

yup, no mention at all of UEFI in the BIOS or boot menu, and the machine can not boot a GPT/EFI windows installer USB, but it can boot an installed UEFI OS ?? the fuck is this ?

[agent_x007]

...
You sure OS was installed in full EFI mode, not Legacy/CSM ?

[GoodBytes]

13 minutes ago, DnFx91 said:

yup, no mention at all of UEFI in the BIOS or boot menu, and the machine can not boot a GPT/EFI windows installer USB, but it can boot an installed UEFI OS ?? the fuck is this ?

What's the motherboard? Some supported EFI  (not UEFI) or partial-EFI, where it was a Frankenstein thing that some motherboard manufacture did to allow 3TB and greater HDDs/partitions to be bootable but still be on BIOS. My gigabyte motherboard has this, but I have the option to disable it on mine, and I have done so, as in my case, being a Frankenstein thing, makes the system take more time to boot (some did better jobs than others).

[agent_x007]

16 minutes ago, GoodBytes said:

What's the motherboard?

MB he listed before (Supermicro X8DAi) : LINK

[GoodBytes]

Just now, agent_x007 said:

MB he listed before (Supermicro X8DAi) : LINK

Oh sorry, I missed it. Thanks!

[GoodBytes]

I see no information on the manual, but the board is from the time where many motherboard did what I mention to support 3TB drives/partition booting. S, if it the drive is indeed GPT, then the option is probably enabled and there is no option to disable it.

[DnFx91]

45 minutes ago, GoodBytes said:

I see no information on the manual, but the board is from the time where many motherboard did what I mention to support 3TB drives/partition booting. S, if it the drive is indeed GPT, then the option is probably enabled and there is no option to disable it.

i think i may have figured it out, i beleive the OS i tried booting on this machine was in fact UEFI/CSM mode, whereas the test installer USB i tried, i burnt as GPT only. Seems that this board simply cant boot UEFI, but can boot CSM (makes sense i guess lol)

[DnFx91]

1 hour ago, agent_x007 said:

...
You sure OS was installed in full EFI mode, not Legacy/CSM ?

i beleive this is what happened 

[agent_x007]

You can make a pendrive for BIOS/UEFI-CSM from Rufus 2.16, because UEFI-CSM allows Legacy booting.

If OS was selected to install with legacy boot option, it will work on new board.
Mystery solved

[DnFx91]

Just now, agent_x007 said:

You can make a pendrive for BIOS/UEFI-CSM from Rufus 2.16.
UEFI-CSM allows Legacy booting.
If OS was selected to install with legacy boot option, it will work on new board.

yeah ive always seen that option in rufus but only ever went full MBR or full GPT, i always went on the snobby logic of "well everything should be UEFI now" and now that is coming back to bite me in the ass lol. However the irony of this, is that this time around, i seem to have either accidentally or somewhat intentionally burnt and installed that OS as CSM, who knows lol. Any other techie guys here find themselves confused over their own work on a daily basis ??

 

Like ill boot up one of my machines, instantly realize that its running KMS, and then get really angry that some arsehole has cracked windows on my lapt..... oh no wait, yeah i cracked that one, to save myself from getting fired

 

 

[TheCherryKing]

It is possible to convert a UEFI Windows installation to Legacy without losing data. I have tried this with Windows 8.1 so I cannot guarantee that it will work with Windows 10.