Windows 10: How set up dual boot with two version of Windows 10

I totally agree Steve, if you have another drive, put your new install on that. But if you want the 2nd install on the same drive, then that`s fine too.

Preferably a solid state drive.

You are assuming you have a solid state drive, all you have to do is look at Disk drives in Device Manager, it should tell you.

Example:

 

The only "trick" is you cannot let the Installer 'see' another installation of Windows or you will have a Dual boot. If you disconnect the drive with the other install when you do the clean install, you will have 2 separate installations and you could delete either one and not affect the other one.

On a clean install you will have a System Reserved partition (which is the active partition and boot files) the C partition and a 'recovery' partition. It is true that a recovery partition is not necessary, but it is small and takes up little room, but it also contains many of the recovery/repair options. Those can be accessed with the installation USB, but it is convenient to have them already there.

 

Ok. Here is Legacy BIOS MBR dual boot drive:





This is how it was created (even though it is Windows 7, it is the same for Windows 10). Note this disk is just one in a multi-drive computer system, all the installations were done with all drives in the computer connected.

1. Start with an unallocated drive - no partitions on it.

2. Boot computer from Windows installation USB flash drive or DVD.

3. Select custom install option. Select the unallocated space. Click next. This will cause Windows to create a System Reserved partition (partition 1 on my drive) and a second partition for the OS. Windows 10 will also create a recovery partition. When you boot the computer from a Windows installation flash drive or DVD and select a completely unallocated drive to install it on, it WILL create a partition with the boot files (System Reserved) on that same drive regardless of what the other drives contain.

4. Boot the computer from this drive (disk 2 in my system). The System Reserved partition will be marked as both the active partition and the system partition. Active tells the legacy BIOS which partition to boot from and system means that is the partition the computer actually booted from. The partition marked as boot is the partition that the OS was actually loaded from.

5. Install MiniTool Partition Wizard Free and do the following:
a. Shrink the partition containing the OS to make room for the second OS. The free space you create will be "unallocated".
b. I converted the OS partition to an extended partition and a logical drive. This is NOT NECESSARY! I only did it because I might want to add more to the disk later and might want to have more than 4 partitions in the future.
c. Create a partition in the unallocated space as large as you want for the second OS. Format this partition as NTFS. <-that part is necessary. I created this partition as a logical partition - this is not necessary, it can also be a primary partition. NOTE: the system partition (in my case, the System Reserved partition) that is marked as active MUST be a primary partition, it cannot be a logical drive.
d. Make sure all the above steps are "applied" and completed.
e. Make sure the bios is set to boot from this drive first and make sure the computer boots into this drive and OS with no user intervention. This drive needs to be the default drive set to boot from in BIOS.

6. Boot the computer from the Windows installation flash drive or DVD that you want to install as the second OS. Select the custom install option. This time select the newly formatted partition that you created for it in step 5c above and click next to install Windows there.

7. Since you selected an existing partition to install to this time, Windows setup will not create new boot files and will not create a new System Reserved partition. Instead it will look for the existing boot files and modify them to set up dual booting. Since the BIOS is set to boot from this drive by default it will find the partition that is marked as active and modify the boot files there.

8. When the computer reboots, you should get a dual boot menu.

NOTES:

I left an unallocated space at the end of the drive. THIS IS NOT NECESSARY! The ONLY reason I left it there is if I want to create yet another partition for data storage, another OS, a custom recovery partition of my own design, or whatever I want. It is perfectly acceptable to use the entire drive, you do not need to leave unallocated space.

The drive has a dedicated System Reserved partition. This partition is very important because it contains the boot files. You want this if you ever plan on deleting one of the installed Operating Systems. You can delete either Operating System and booting the computer will not be affected.

If you do not use a System Reserved partition dedicated to being the active partition, then the boot files will be on one of the partitions containing an Operating System. Delete the OS partition and your computer won't boot from that drive.

I hope this helps.

 

That`s pretty much exactly what I told him to do in reply #39, waiting to see his next shot of Disk Management.

I wanted him to create the unallocated space 1st and then post a shot of DM before he proceeded.

 

Hello folks! Still not feeling well - maybe later today I'll get to the last instructions and send the DM jpg. Thanks........

 

OK, I'm feeling better and would like to get started today. But, even though I certainly appreciate all the feedback, I'm now very confused as to whose instructions I should follow. I wouldn't have any trouble removing or unplugging my second drive (data only). Also, when I'm done transferring all my apps and settings to the clean install, I would like to be able to easily remove the current version of Windows 10. @AddRAM, what should I do please?

 

Let`s get that 2nd partition created or at least show me the unallocated space on Disk 0 with Partition Wizard, we will take it 1 step at a time. *Smile

And yes, unplug all other hard drives while we do this. Just the power cable.

After you get that done, post a new shot of Disk Management.

And you mentioned transferring Apps, you can`t transfer apps, programs, etc. You will have to reinstall them.

 

See comments below...........

I know I'll have to reinstall them - but I have no choice at this point. I just hope I can get up and running soon. I'll install the most important apps first - then will have to switch back to the old install to do my work (temporarily).

 

Did you create your 2nd partition yet ?

Where are you with this ?

What`s going on ?

 

OK, here's the DM jpeg. AddRAM, FYI: I have removed the second drive before.
Attachment 119119

 

OK, now disconnect Disk 1,2,3 and do your clean install to the unallocated space.

Post a shot of DM when you`re done.

And you`ll have no problem removing the old install when you`re ready, because your System Reserved partition is marked Active and contains the system files.

But you should remove the letter from it.

Your Data drive (D) is marked Active, it should not be, we`ll fix that later.

 

Install & Update completed. Do I have to install updated drivers? What's next?
Attachment 119164

 

OK, we`re gonna start over, because the installer created an extended partition and installed W10 on a Logical drive.

I personally would not leave it like that. Others may think it`s fine. And please speak up.

Go into your old install and use Partition Wizard to delete F back to unallocated space and create a Primary partition, then re install Windows 10.

You should then have 4 Primary partitions and there should be dark blue all the way across the top of Disk 0.

 

I'll do as you recommend - but tomorrow I spend with my wife so I won't be able to get it done until tomorrow night or the day after. Thanks!

 

There is nothing wrong with it being in a logical drive in an extended partition. But there is a much easier way to change it, if desired to do so. Install MiniTool Partition Wizard and just convert the partition to primary.

MiniTool Partition Wizard | Best partition magic alternative for Windows PC and Server

See my example partition: