Strange Partitions after W10 install on new build

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  1. Nomadski
    Posts : 20
    Windows 10 Pro v19042.1052
       New #1

    Strange Partitions after W10 install on new build


    I've just built a new PC and installed W10 from a USB after using the W10 creation tool on my old build.

    Everything seemed to install fine but I noticed some quirks (like start button and key not doing anything) so I decided to do a reset.

    That completed but now I've noticed my NVME 1TB OS drive has it's System Reserved partition in my PC with a drive letter. When I go into Disk Management I notice the drive has a System Reserved partition with letter, the main partition with letter, a 100mb EFI system partition and a 513mb Recovery Partition.

    I didn't notice W10 having so many partitions on my last build? And why did I get a System Partition Drive letter?

    Strange Partitions after W10 install on new build-screenshot-02_08_2020-15_52_40.pngStrange Partitions after W10 install on new build-screenshot-02_08_2020-15_53_15.png
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  3. dalchina
    Posts : 43,122
    Win 10 Pro (22H2) (2nd PC is 22H2)
       New #2

    Hi, a UEFI installation typically has 4 partitions. You usually need a 3rd party partition manager to see the 4th, but it's shown in your case.

    There seems no Active partition on Disk 0. The system reserved partition should not have a drive letter.

    Did you clean install to unallocated space on disk?

    I'm wondering about the 16Mb partition on Disk 1 - older builds have a 16Mb System Reserved partition (not shown by Disk Management by design) on the system disk.

    Please post a screenshot with a 3rd party partition manager expanding all columns as necessary to show all text.
    Strange Partitions after W10 install on new build-1.png

    Note the old/redundant Recovery partition at the start- the one in use is after C: - that's typical of an installation upgraded from an older build. (MS has now changed this to put the Recovery partition after C: as it should have been)

    The forum prompted you to specify your full build number (so we don't have to keep asking).
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  4. Nomadski
    Posts : 20
    Windows 10 Pro v19042.1052
    Thread Starter
       New #3

    dalchina said:
    Hi, a UEFI installation typically has 4 partitions. You usually need a 3rd party partition manager to see the 4th, but it's shown in your case.

    There seems no Active partition on Disk 0. The system reserved partition should not have a drive letter.

    Did you clean install to unallocated space on disk?

    I'm wondering about the 16Mb partition on Disk 1 - older builds have a 16Mb System Reserved partition (not shown by Disk Management by design) on the system disk.

    Please post a screenshot with a 3rd party partition manager expanding all columns as necessary to show all text.
    Strange Partitions after W10 install on new build-1.png

    Note the old/redundant Recovery partition at the start- the one in use is after C: - that's typical of an installation upgraded from an older build. (MS has now changed this to put the Recovery partition after C: as it should have been)

    The forum prompted you to specify your full build number (so we don't have to keep asking).
    Sorry, I updated system specs and put build number (v19041.388) in OS part.

    I managed to "hide" the drive letter away from ThisPC for the System Reserved partition, so i no longer see it in This PC.

    My previous build was the free updated digital licence version of Windows 10 Pro given by Microsoft to Windows 8.1 Pro users (which was a upgrade from Windows 8 Pro).

    ive never used a 3rd party Partition Manager before so excuse me if what I did isn't what you asked for but here is a screenshot from one I just installed...

    Strange Partitions after W10 install on new build-screenshot-02_08_2020-17_00_57.png
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  6. Megahertz
    Posts : 6,392
    Windows 11 Pro - Windows 7 HP - Lubuntu
       New #4

    You build a new PC but used a drive from another computer that was upgraded to Win 10 from Win 8.x?

    System reserved partition normally are created by OEM computers to have some tools.
    Did you ever do a clean install (deleting all partitions) on the disk?
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  7. cereberus
    Posts : 15,496
    Windows10
       New #5

    dalchina said:
    Hi, a UEFI installation typically has 4 partitions. You usually need a 3rd party partition manager to see the 4th, but it's shown in your case.

    There seems no Active partition on Disk 0. The system reserved partition should not have a drive letter.

    Did you clean install to unallocated space on disk?

    I'm wondering about the 16Mb partition on Disk 1 - older builds have a 16Mb System Reserved partition (not shown by Disk Management by design) on the system disk.

    Please post a screenshot with a 3rd party partition manager expanding all columns as necessary to show all text.
    Strange Partitions after W10 install on new build-1.png

    Note the old/redundant Recovery partition at the start- the one in use is after C: - that's typical of an installation upgraded from an older build. (MS has now changed this to put the Recovery partition after C: as it should have been)

    The forum prompted you to specify your full build number (so we don't have to keep asking).
    There is something weird here.

    That first 50MB partition looks like a hangover from an old mbr installation which is a bit odd as the installation has upgraded to a UEFI installation. I am puzzled how this can be as drive would have to be GPT for 64bit. It is not big enough to be a former recovery partition. They are usually around 450+ GB.



    Either way that first partition is redundant.
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  8. topgundcp
    Posts : 2,799
    Linux Mint 20.1 Win10Prox64
       New #6

    Megahertz said:
    You build a new PC but used a drive from another computer that was upgraded to Win 10 from Win 8.x?

    System reserved partition normally are created by OEM computers to have some tools.
    Did you ever do a clean install (deleting all partitions) on the disk?
    This is not true. If you install Windows 10 using MBR disk style then it will create A System Reserved partition.
    From the disk layout. I think OP initially installed Windows using MBR partition then later convert it to GPT.

    The 50MB System Resreved partition is created starting with Windows 10 Version 2004, the disk layout for MBR is:
    50MB Resreved partition, C drive then 505MB Recovery.

    For GPT Disk:
    100 MB EFI partition, 16MB MSR, C drive then 505MB Recovery.

    And as mention above, this 50 MB Reserved partition is no longer used. The EFI partition is clearly stated that it is System and active, meaning it is booted from this partition. It does not mean the partition is set to active as in the case for MBR disk.
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  9. Nomadski
    Posts : 20
    Windows 10 Pro v19042.1052
    Thread Starter
       New #7

    Megahertz said:
    You build a new PC but used a drive from another computer that was upgraded to Win 10 from Win 8.x?

    System reserved partition normally are created by OEM computers to have some tools.
    Did you ever do a clean install (deleting all partitions) on the disk?
    The install was on a brand new NVME drive but see below...

    topgundcp said:
    This is not true. If you install Windows 10 using MBR disk style then it will create A System Reserved partition.
    From the disk layout. I think OP initially installed Windows using MBR partition then later convert it to GPT.

    The 50MB System Resreved partition is created starting with Windows 10 Version 2004, the disk layout for MBR is:
    50MB Resreved partition, C drive then 505MB Recovery.

    For GPT Disk:
    100 MB EFI partition, 16MB MSR, C drive then 505MB Recovery.
    Sorry i'm not very techie but I'll try and explain what happened.

    I was on a 64bit W10 install which was an upgrade from many years ago and I just made a USB W10 USB install disk from Microsofts website. I installed W10 and noticed some strange things happening (Windows key nor the bottom left icon worked, I opened a folder and it opened behind the previous window instead of in front etc).

    So with it being a new install I checked to see OS details and I noticed it said "Legacy" rather than "UEFI" - presumably because the new mobo had CMF enabled?

    Anyway I followed instructions here - How to Convert Legacy BIOS to UEFI in Windows 10 - Make Tech Easier to return to UEFI, switched CMF off in BIOS and then reset Windows 10.

    The final reset didn't do anything to the partitioning of the drive. I wonder if I should have run W10 install from USB stick again?

    I notice looking at the website (above) that below it mentions GPT table so am thinking you guys are on the right track.

    Sorry if the above should have been detailed before.

    What would you recommend I do?
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  10. topgundcp
    Posts : 2,799
    Linux Mint 20.1 Win10Prox64
       New #8

    @Nomadski,
    Since Windows 7, the minimum size of the Reserved partition is 100MB and keep growing to larger size 300, 350, 400 etc.... Your Reserved partition is 50MB, this only happens if you first install Windows 10 version 2004 with MBR disk style.

    Here's my Windows 10 version 2004 with MBR disk style installation:
    Strange Partitions after W10 install on new build-2020-08-02_162311.jpg

    and Windows 10 version 2004 using GPT disk style:
    Strange Partitions after W10 install on new build-snapshot_20-08-02_16-27-39.png
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  12. Megahertz
    Posts : 6,392
    Windows 11 Pro - Windows 7 HP - Lubuntu
       New #9

    Do it right from the beginning. Do a Clean Install Windows 10

    To install as UEFI you must boot the Win 10 installation drive (DVD or USB) as UEFI, not legacy.
    During POST, launch the boot menu. The USB installation drive options will be the USB and UEFI - USB. Choose the UEFI - USB.

    Once you boot from the installation disk as UEFI, go to install and delete ALL partitions till you have one and only one unallocated space and then proceed.
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  13. Nomadski
    Posts : 20
    Windows 10 Pro v19042.1052
    Thread Starter
       New #10

    Megahertz said:
    Do it right from the beginning. Do a Clean Install Windows 10

    To install as UEFI you must boot the Win 10 installation drive (DVD or USB) as UEFI, not legacy.
    During POST, launch the boot menu. The USB installation drive options will be the USB and UEFI - USB. Choose the UEFI - USB.

    Once you boot from the installation disk as UEFI, go to install and delete ALL partitions till you have one and only one unallocated space and then proceed.
    I remember seeing that and wondering what it meant, I clicked on USB.

    Will my BIOS revert anything (ie reenable CMF CSM) or will those settings stay put?
    Last edited by Nomadski; 02 Aug 2020 at 19:50.
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