John Dulak <Johnd@Booogus.com> wrote:

> VanguardLH wrote:
>
>> John Dulak <Johnd@Booogus.com> wrote:
>>
>>> My primary computer is a desktop. It was purchased as an "Off Lease"
>>> machine that came with Windows 10 installed. Since I absolutely
>>> loathe the user interface of Windows 10 I installed Windows XP on a
>>> separate hard drive but kept the hard drive with the Windows 10
>>> install for occasional use.
>>>
>>> To use Windows 10 I shut everything off open the case, unplug the XP drive, plug
>>> in the Windows 10 drive and boot. The oddity happens when I reverse the above
>>> steps to return to Windows XP. When I boot from the XP drive for the first time
>>> I get a message "No Operating System Found"!! I then power cycle the system and
>>> everything is fine with XP.
>>>
>>> Since I rarely use Windows 10 this is not a large problem but it IS puzzling and
>>> any explanation would be comforting.
>>
>> Presumably the drives are internal. When removing or replacing the
>> drives to switch between OSes, they are inside the case and connecting
>> to headers on the motherboard. Are you connecting the drives to the
>> SAME header on the motherboard?
>
> Each drive connects to the same set of cables and are never BOTH
> connected at the same time. This is a Lenovo M91p and, since it had
> aprevious owner perhaps they installed UEFI somewhere along the line.
> XP *always* loads correctly on the second try and it just seems
> wierd.
>
>>
>> Windows 10 works with UEFI. Windows XP is incompatible with UEFI.
>>
>> https://en.wikipedia.org/wiki/UEFI
>>
>> You didn't identify your motherboard for others to know if it only
>> supports MBR, if it supports UEFI, or supports UEFI but configured to
>> boot in MBR/BIOS mode.
>>
>> https://learn.microsoft.com/en-us/windows-hardware/manufacture/desktop/boot-to-uefi-mode-or-legacy-bios-mode?view=windows-11
>>

Go into the BIOS settings. Check the devices listed for boot order.
Also check if the UEFI BIOS is configured to boot in MBR mode. You'll
need to use MBR mode for both Windows XP and Windows 10 during booting.
That also means the partitions on your Win10 HDD need to have an MBR
section.

The boot process between MBR and UEFI devices is different:

https://en.wikipedia.org/wiki/UEFI#Boot_stages

With MBR, the BIOS looks the first drive in the boot order that has an
MBR partition table, and looks for which of the 4 primary partition
records in the MBR partition table is marked active (the one to boot
from). It then reads the first sector of that partition to use as the
boot loader for the OS in that partition.

https://www.scaler.com/topics/operating-system/master-boot-record/

Looks like your computer supports UEFI, and tis likely the partitions on
the Win10 drive are GPT (Guid Partition Table) partitions.

https://www.scaler.com/topics/operating-system/master-boot-record/

https://en.wikipedia.org/wiki/GUID_Partition_Table

You're mixing two different boot schemes along with different partition
types. The UEFI works with the GPT partitions on the Win10 drive, even
if the partitions change order. MBR is more archaic and sensitive to
partition order and MBR boot sector location. You're booting using UEFI
with it having records for the Win10 drive, and then switching drives,
so the UEFI fails in its guessing.

My guess is you will need to reformat the GPT partitions on the Win10
HDD from GPT to MBR partitions.

https://learn.microsoft.com/en-us/windows-server/storage/disk-management/change-a-gpt-disk-into-an-mbr-disk

Probably easier to use a partition manager (e.g., Easeus Partition
Magic, Minitool Partition Manager, etc). However, you didn't mention
the size of the partitions on the Win10 HDD. MBR mode does not support
partitions larger than 2 TB.

https://www.intel.com/content/www/us/en/support/articles/000007722/server-products/sasraid.html
An MBR has a partition table describing the partitions of a storage
device. The maximum size of an MBR partition cannot exceed 2 TB (2.19
TB). MBRs are constrained by supporting only four main partitions and
a volume size of less than 2 TB. These constraints inhibit their use
in larger volume sizes.

The HDD can be bigger than 2 TB, but no partition on it can be larger
than 2 TB when using MBR mode (a restriction on the number of sectors
that can be defined within a partition record in the MBR partition
table). This is usually resolved by having the OS and apps in one 2 TB
partition, and all data stored in other partitions on the same HDD.

Some 3rd-party partition managers can convert from GPT partitions to MBR
partitions without formatting which means no data loss; else, as I
recall, the typical GPT-to-MBR conversion destroys (deletes) the GPT
partitions, creates new MBR partitions, and the OS and apps are
installed onto the MBR partitions, and the data recovered from backups.

https://www.easeus.com/partition-master/change-gpt-disk-to-mbr-disk-without-format.html

Alas, often this conversion is not free.

https://www.easeus.com/partition-manager/comparison.html
https://www.diskpart.com/compare-edition.html

The free editions do not include conversion between GPT and MBR
partitioning.

https://www.partitionwizard.com/comparison.html

That table for free Minitool Partition Manager says it will convert from
GPT to MBR. Because of how they are playing with partitioning which
could fail, I'd make sure any data you have on your Win10 HDD has been
copied elsewhere to restore later.

I think GPartd is free and open source. I've not used it. Mostly using
by Linux folks. You'd need a bootable CD or USB drive (and it listed in
the boot order in the BIOS) to load an OS (Linux) that has GParted. You
get a bootable image of Gparted on a Linux (Debian) that you boot from
to do the partitioning tasks. Someone else will have to point to an
online article facilitating the GParted process to convert from GPT to
MBR partitioning. The ones I found had too many Linux commands rather
than hiding the details inside the other GUI partitioning tools.

If you have the installation media for Win10, and since it's a playtoy
setup that isn't critical, you could do the GPT-to-MBR convert, lose
everything in the old GPT partitions, and install Win10 in the new
partitions. I wouldn't trust the Win10 installer to create MBR
partitions. It will see your computer BIOS/UEFI supports GPT
partitions, and likely default to creating GPT partitions. Convert from
GPT to just *1* MBR partition (that encompasses the entire HDD, or up to
2 TB of the HDD), and during Win10 install have it reuse the existing
MBR partition instead of insisting on its own multi-partition (and
perhaps GPT) layout.

After you convert your Win10 HDD into MBR partitions, you then go into
BIOS to change UEFI mode to MBR (legacy) mode. You'll have to read your
computer's manual, or check their online help on the navigation steps in
the BIOS to change from UEFI to MBR (legacy) mode.

That's a lot of work for an "occasional" switch to Windows 10. You
might just leave it as it is where you have to double boot to get the
UEFI firmware to find the active partition in the MBR partition table
when you go back to the WinXP HDD. How much this is a nuisance depends
on how often you switch back and forth between the WinXP and Win10 HDDs.
And I'm not guaranteeing anything about the above processes. I've never
converted from GPT back to MBR, and changed the BIOS from UEFI to legacy
(MBR) mode. I've only gone forward, not backward.

For me, if I had an occasional need to use or educate on Windows 10, but
have Windows XP as my primary platform, I'd use Virtualbox (free). Run
Windows XP as the host OS, create a VM drive in Vbox, and install
Windows 10 inside the Vbox VM drive. OSes inside VMs that emulate all
hardware except for the CPUs and with pass-through drivers to hardware
don't run as fast as OSes the native hardware, but the performance hit
may be insignificant to however you plan on using Windows 10.

https://www.virtualbox.org/

With VMs (virtual machines), you don't have to open the system case to
swap out drives nor have to reboot the computer. It's been several
years since I last used Virtualbox, so I don't know if Windows XP is
still supported as the host OS where the VMM (Virtual Machine Manager)
runs that loads the VMs. They have their own community forums where you
can ask if Windows XP is still supported as the host OS. You might have
to move to an older version of Vbox to get Windows XP support; see
https://www.virtualbox.org/wiki/Download_Old_Builds. I think WinXP
support was dropped in Vbox 5.x. Looks like support for 32-bit host
OSes was dropped in Vbox 6.x. When you say "Windows XP", I assume you
mean the 32-bit versions, not the 64-bit frankenjob version that used
Windows 2003 server as the codebase and pasted a Windows XP atop of that
for x80-x64 AMD/Intel architectures (which was incompatible with many
non-server programs), or the special Itanium IA-64 CPUs. Presumably you
have a 32-bit Windows XP version. As I recall, Vbox 6.x (until a later
sub-version) had a problem on Windows setups where Hyper-V was enabled.
The 2 hypervisors conflicted with each other. The first cure was to
disable Hyper-V in the BIOS. The second was a new version of Vbox 6.x
that would detect HyperV was enabled, and use HyperV instead of Vbox's
own VMM (which is faster than Microsoft's HyperV). But to run Vbox on
Windows XP as the host OS, I think you're stuck using pre-5.0 versions
of Virtualbox, like 4.3. Ask their community forum.

I do remember after installing Vbox, and creating a VM into which an OS
got installed, of having to install some extensions pack of Vbox into
the VM to make things smoother/faster, like getting rid of jitter in
mouse cursor movement. I don't remember when the extension pack became
available in which version of Vbox. If you have to go back to Vbox 4.3,
then look at https://www.virtualbox.org/wiki/Download_Old_Builds_4_3 on
getting the extensions pack.