How to create - or convert - partitions in a Legacy MBR/BIOS setup

I have just upgraded a Lenovo T430 laptop from Win7 Pro to Win10 Pro (version 20H2) with the excellent help of Brink's tutorial.

I chose an in-place upgrade as I wanted to retain some of the settings and apps from the Win7 setup (I have no critical personal data on this machine). This meant that much of the OEM Lenovo tools and apps were also retained.

I kept the Legacy/MBR disk configuration because I prefer - and am more familar with - that than UEFI/GPT.

I left the partitioning to the upgrade process. All worked well, and Win10 now runs happily. I was however slightly surprised to see that the disk has four primary partitions. This is a bit tiresome, as I plan to install Linux in a dual boot setup (as I have on other computers). For that I need to create more partitions. But at present I cannot do so!

Linux will run from a logical partition. But in order to modify the existing partition arrangements (basically to create an extended partition and more logical partitions within it for Linux), I will have to either delete or convert one of the four existing primary partitions.

Here is a screenshot from Win10 Disk Management of my current disk partitioning:



Now..... obviously I cannot mess with the System Reserved primary partition (D: - or sda1 in Linux-speak). I will have scope to shrink the C: partition (sda3) where Win10 resides, in order to make space for Linux. But before doing so I will have to do something with one or other of the two remaining primary partitions, because I need to create an extended partition, with logical partitions inside it) for Linux.

So.... I have a 12.55GB "Recovery" partition (Q: - or sda2) which is 96% full. And I have another partition of just 624MB which has no drive letter in the Windows system (sda4 in Linux). It is described as 'Recovery partition' and is totally empty. I cannot figure out how and why there are these two partitions - both supposedly to do with recovery.

NB As a Linux user (but no expert) I have looked at the disk using GParted, and I note that this last partition, sda4, has the "diag" flag on it. Not sure I fully understand what that implies.....

Before embarking on this, I'd welcome advice. It seems to me I have two options:

1) delete this last, unlabelled 624MB primary partition to make it 'unallocated space'; then shrink the adjacent C: partition as much as Win10 will allow, to give me more space; and create a new extended partition in that space - in which i can then organise the necessary further logical partitions needed for a Linux install. Or....

2) "convert" that unlabelled partition from primary to logical (which I think will need 3rd party software like Easeus or Minitool Partition Wizard); then shrink the C: partition, and expand and reconfigure the extended/logical partition into that space.

The first route seems the simpler and easier (I don't entirely trust third party tools). But is there anything I have overlooked? I am just puzzled as to why this fourth unlabelled - supposedly recovery - partition exists, and uncertain as to whether I should mess with it or the 'diag' flag it carries.

Any comments and advice will be appreciated. I believe in the "check three times, measure twice, cut once" approach, especially when working on disk partitions!

topgundcp said:

Based on the screen shot.

1. D: => Partition 1 (sda1) is currently not used at all.
2. Q: => Partition 2 (sda2) contains Windows 7 OS from manufacturer that the PC was installed with.
3. C: => Partition 3 (sda3) contains Windows OS, Boot Manager + BCD to boot Windows 10 from.
4. No letter assigned => Partition 4 (sda4) is Windows 10 Recovery Partition: Contains WinRe.wim for Win 10 troubleshooting. It is hidden but not empty. The diag flag set in Gparted indicates that this partition type id is = 27 ie. a Recovery Partition Type. For other partitions, they would be 07 as basic type ID.

It's comforting to have advice from a member who (like me) works with both Windows 10 and Linux Mint. But I fear I'm already getting a bit confused - not least because I don't have the expertise to delve into each partition to discover what exactly resides in each of them!

- If the System Reserved partition (D: or sda1) is empty and unused (and it is very small at 100MB) , then how come it is showing 30% used? What's taking up 30MB in there? Is it actually not needed? See the notes under step 14 in this tutorial which says there is a choice about whether to have a System Reserved partition or not, that it contains the Boot Manager code and the BCD and other stuff, and the recommendation was to have one! So I did.

FWIW all my laptops seem to have a small sda1 System Reserved partition at the start of the disk. I thought this was essential and a default, and not something to tamper with.

- if Q: (sda2), labelled Recovery, contains Win7, how do you know? Not that I'm disputing it. Would this be in effect a system image of the original Win7 OS, saved there, preexisting, from OEM - and placed there as part of the original configuration? I don't know how Lenovo sets up the "support/recovery" arrangements on their computers.....

This raises the question of what purpose is now served by Q: (sda2)? If Win7 has been upgraded/replaced, as noted, and there is a separate Win10 recovery partition at the unlabelled sda4, are the contents of Q: (and it is almost full!) still needed? Is that the partition I should be deleting to make space for a new extended partition - or converting into such a partition?

I do know that following the Win7 to Win10 upgrade, the "old" Win7 files are all saved by the Microsoft upgrade process, at least for a while. I haven't 'purged' them. But I assumed these Win7.old files would be somewhere on the C: drive, not in the Recovery partition at Q:.

- I agree that C: (sda3) has pretty much all that is required to boot and run the now-installed Win10 OS. Does it not need anything from sda1? My knowledge is limited - but see the comment above about the System Reserved partition. I also understood that the first bit of the Microsoft Boot Manager, or the MBR, is in sda (ie hidden and in the very first sectors of the disk)...

- Interesting that Partition 4 (sda4) is the Win10 recovery partition - presumably created during the Win7 to Win10 upgrade. As such, am I right to think it is not the one I should be looking at deleting/converting/replacing....

So I'm still a bit stuck. How and where do I create an extended partition into which I can install Linux Mint?

Thank you, topgundcp, for those very helpful further suggestions and explanations.

My careless mistake to interpret your comment that sda1 (D:) is "not used" as indicating it was empty.

I cannot see any likelihood that I might want to revert to Win7, as it is EOL now; and the upgrade to Win10 seems to have worked, which gives me that as the Windows OS on this machine.

I fully accept your advice that the unlabelled partition (sda4) ought to be kept, if that is what enables a Win10 recovery. It has to be sensible to have some sort of recovery option.

Being inclined to cautious rather than radical options, I'm wondering - why not leave sda1 (System Reserved) as-is? Then save the contents of sda2 (the Q: Recovery partition) to an external drive just in case; delete that partition to give unallocated space; shrink and move the existing sda3 (C:) and also the unnamed (sda4) recovery to the left .... if indeed I need to. And then create a new extended partition for Linux Mint in the space remaining. Is renumbering necessary?

Or indeed - even simpler, just delete sda2 (Q:) after transferring the contents to an external location; shrink sda3 (C: ) as far as Win10 will allow; and set up an extended partition for Mint in the space where sda2 used to be. That saves moving the other two partitions - the Win10 (sda3) and its recovery partition (sda4) - sideways and relabelling/renumbering them. A bit less tidy - but does it matter if the partitions are not lined up in numerical order?

As for the Mint install, yes indeed, the 'something else' option with Grub in the same partition as Mint and EasyBCD to create and manage the dual boot. That's what I have on a couple of other laptops - in those cases I didn't need to remove or reconfigure existing partitions, just set up an extended one, as these other machines didn't already have four primary paritions.

You can delete the 100mb "system reserved" partition , it is not used on your system and is redundant. That will free up the partition table slot you need to create an extended partition.

save the contents of sda2 (the Q: Recovery partition) to an external drive just in case; delete that partition to give unallocated space; shrink and move the existing sda3 (C:) and also the unnamed (sda4) recovery to the left .... if indeed I need to. And then create a new extended partition for Linux Mint in the space remaining.

Yes, you could do that with a 3rd party partition manager. Depending which partition manager you use, you might need to adjust the bcd store afterwards.

SIW2 said:

You can delete the 100mb "system reserved" partition , it is not used on your system and is redundant. That will free up the partition table slot you need to create an extended partition......

Yes, you could do that with a 3rd party partition manager. Depending which partition manager you use, you might need to adjust the bcd store afterwards.

Aargh, another little twist! "........you might need to adjust the BCD store"? That's uncharted waters for me.

If the System Reserved partition REALLY is redundant, then I am ready to delete it to create a new slot. Once it's gone, it's gone.... so I need to be very very sure of what I'm doing.

Just for info, what I normally do to manage partitions is to use Windows disk manager to shrink (or expand) partitions which are used or needed by Windows. Then I use GParted (which is available as part of the Linux install session) to create/expand/move the partitions required for the Linux OS.

Renumbering them is however not something I think I have ever done (and I wouldn't know where to start on adjusting the bcd store, if that were to be necessary).