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Help with Dual Booting Windows 11 and Windows XP

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First post, by Barley

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I tried asking this on Reddit Windows XP sub but haven't gotten an answer.

I am in the throws of my next project, which is to dual boot Windows 11 and Windows XP with each OS having its own SSD.

I'm using an X79 board and GTX 980 Ti.

BIOS is set to Legacy/CSM mode.

I got Windows XP installed and working on SSD 1. SSD 1 is first in BIOS boot order.

Then I got Windows 11 installed and working on SSD 2. I later realized it defaulted to GPT/EFI mode (the default for Windows 11). The PC automatically started to boot Windows 11 without giving the option to boot Windows XP.

I installed EasyBCD in Windows 11 but ran into an error that it could not add Windows XP because Windows 11 was in EFI mode.

I added SSD1 to the EasyBCD settings anyway, using Windows 7 in the drop down (knowing it was wrong...I just wanted to try it out to make some progress/troubleshoot), and predictably got an error when I tried to boot into Windows XP using the blue boot menu at startup.

I then removed SSD 1 from the EasyBCD settings, and here is where things get interesting. When I rebooted, I got a text-based black screen Windows Boot Manager page, with only Windows 11 in the menu. If I selected Windows 11, it would boot into Windows 11, but if I hit ESC during this menu, it would boot into Windows XP! Granted, it did run a disk check first, but didn't find any errors, and the disk check has not run again.

So technically I am dual booting now, but it seems like I'm not doing it correctly. Just before I experienced this roundabout way to dual boot, I had been ready to reinstall Windows 11 in MBR mode using Rufus. Is that really what I should be doing, or is my current situation sustainable? Really, I'd like to know why it's working right now.

Thanks for your help, and let me know if any of this does not make sense!

Reply 1 of 4, by Barley

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I decided to reinstall windows XP, then reinstall Windows 11, but using MBR partitioning. After some trial and error with EasyBCD, I got the dual booting to work.

Reply 2 of 4, by AncapDude

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Didn't know Win11 still supports BIOS. Thought it was UEFI only. Interesting.

Reply 3 of 4, by Barley

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AncapDude wrote on 2025-08-19, 02:52:

Didn't know Win11 still supports BIOS. Thought it was UEFI only. Interesting.

Microsoft sure doesn't advertise it. I created a Win11 USB boot image in Rufus, which gives you the option of using BIOS/MBR.

Reply 4 of 4, by LarryM

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You wrote :
Didn't know Win11 still supports BIOS. Thought it was UEFI only. Interesting.

Yes win11 supports BIOS (Legacy/CSM mode)

Then there is no problem to install win11 64bit / winxp sp3 32bit
it works even on the same (alligned) harddisk ; yes ! - win11 works with MBR - without UEFI !

GPT-Mode is a crazy thing with WinXP - I dont recommend

If you have a bigger ssd / harddisk than 2 TB - I have a interesting
solution.

You can expand your MBR (SATA) Drive (at least) to 4 TB with ease.

I use winXP SP3 32-bit (primary) and GPT makes a lot of problems.

Now I read :

https://care.acronis.com/s/article/38937-True … jk0&ckattempt=1

Symptoms
An operation attempt with a drive larger than 2 TB fails with following error:
Please install Virtual Disk driver manually

http://dl2.acronis.com/u/kb/VirtualDiskSetup.msi

i think the latest version is from 2014

There are only few informations in internet about this tool.

The program opens the space above 2TB as additional "2TB" virtual disk.
You see this in "Computermanagment". They are "primary" !!

In Explorer you see the full capacity of all your partitions.

I have tested sucessfully with Seagate 4 TB SATA
ST4000DM004 > 4K physical emulated at 512-byte sectors
Barracuda SATA Product Manual 100805918, Rev. P December 2020

You DONT need Seagate Extended Capacity Manager.

Another person tested with a WD30EZRX 3 TB WD Caviar Green
https://windowsforum.com/threads/hd-disk-mana … 40/#post-646781
Interface SATA 6 Gb/s
Advanced Format (AF) Yes

So it should work with disks from all manufacturers.

I have tested on a "old" MSI Board without UEFI.

I have tested with XP SP3 32bit , W2k3 64bit and Win11 23h2 64bit
(yes ! - win11 works with MBR - without UEFI !)

I have not tested with SSD.

I make a full capacity test with h2testw_1.4 without errors
4 TB write and test takes about 13 hours !!

It would interesting for me if the tool works with capacity more than 4 TB.
Maybe someone can test it.

But in "future" XP-users have another problem if
the disk provides no more 512e emulation
http://wp.xin.at/archives/2581
and if there are no more actual browsers

Greetings : LarryM from germany

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