1.    26 Apr 2016 #1
    Join Date : Jul 2015
    Pacific Northwest, USA
    Posts : 387
    Win10 x64 Pro -2 desktops, 1 laptop

    BIOS or EUFI for clean install?


    I did an upgrade in place from Win7 to Win10 on a PC. The PC is is showing some odd behavior so I'm considering doing a clean reinstall of Win10. The PC currently uses BIOS but the MB supports EUFI. If I do the clean reinstall should I switch from BIOS to EUFI?

    If I switch, what things do I need to consider? I've read conflicting info about the system drive. Some web sites say the drive must be formatted using GTP rather than MBR; other sites say there is no reason to reformat. Which is true? I assume BIOS / EUFI doesn't effect the non-system drives at all, but I never trust my assumptions. Is there anything I need to worry about there?
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  2.    26 Apr 2016 #2
    Join Date : May 2015
    Smyrna, TN
    Posts : 306
    Win 10 Pro 64

    Here is a good article regarding your question............this might help clear it up some for you...

    Differences Between UEFI and BIOS

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  3.    26 Apr 2016 #3
    Join Date : Jul 2015
    Pacific Northwest, USA
    Posts : 387
    Win10 x64 Pro -2 desktops, 1 laptop
    Thread Starter

    That link helped - not only for the information the article contained, but also because it provided me with more terms to search.

    I now understand that usable non-system disks are formatted either as MBR or GPT even though the the MBR-formated disk has no master boot record (or if it has one, it is not used). It's all about the partitioning rather than about the boot record. And Windows (all the way back to XP) can read from and write to a GPT disk. But booting from a GTP disk requires EUFI, and (at least for Windows) EUFI requires booting from a GPT disk.

    I'm still not sure about restoring partitions, though. Since MBR and GPT partitions have different kinds of identifiers, I'm not sure a restore utility would know how to map them. I guess that's a question for the utility vendor.
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  4.    26 Apr 2016 #4
    Join Date : May 2015
    Smyrna, TN
    Posts : 306
    Win 10 Pro 64

    Here is another interesting article.....might help answer a few more of your questions....

    Convert Windows 10 from old MBR (BIOS) to UEFI.....
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  5.    26 Apr 2016 #5
    Join Date : Dec 2015
    Posts : 6,444
    Windows10

    Modern image tools easily handle UEFI (even MS built in tool). In fact, UEFI is better as the boot sectors are always separate from system drive by design.

    Lots of reasons for UEFI e.g.

    1) handles drives over 2.2TB as OS drive.

    2) Allows more than 4 primary partitions

    3) More secure (assuming you keep secure boot on)

    So always go for UEFI if it can be used.
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  6.    26 Apr 2016 #6
    Join Date : Feb 2016
    Posts : 51
    Windows 10 Home x64

    Firstly, you need a thumb drive 8GB and fat32 format. Then, you switch the BIOS to auto mode. If can not, choose UEFI. If can not, select legacy. You can switch it whenever you like. The main thing is thumb drive is fat32 format ( installer ).
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  7.    27 Apr 2016 #7
    Join Date : Aug 2015
    Penn's Woods
    Posts : 1,288
    Windows 10 Home

    Quote Originally Posted by pokeefe0001 View Post
    ...
    If I switch, what things do I need to consider?...
    Using Win10 install media gotten either via Media Creation Tool or downloaded from TechBench, are you going to use a DVD or USB flash drive?

    Two main things to consider are:

    1) Whether Win10 installs as MBR (for BIOS/Legacy booting) or GPT (for UEFI booting) will be determined by how you set the BIOS, i.e., if you want to go to GPT disk scheme, set the BIOS for UEFI boot and boot the Win10 install media as UEFI (Media Creation Tool will create a USB flash drive that's bootable both UEFI and legacy) and

    2) To do a truly clean install, you need to select Custom Install after booting from the Win10 media and starting install and then delete all partitions on your system disk (best to have all other disks except boot device disconnected) until all space is unallocated, then Win10 will create all partitions it needs on the unallocated disk according to how you booted the install media (GPT for EUFI, MBR for legacy boot).
    Last edited by Word Man; 27 Apr 2016 at 09:56. Reason: typo
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  8.    27 Apr 2016 #8
    Join Date : Aug 2015
    Maine
    Posts : 40,228
    Windows10Pro 64Bit

    @pokeefe0001
    Reading the spec's on your motherboard ASUS Z87-A According to ASUS site this board supports UEFI So in that case you should follow the instructions Word Man has suggested. GTP style partitions.
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  9.    27 Apr 2016 #9
    Join Date : Jul 2015
    Pacific Northwest, USA
    Posts : 387
    Win10 x64 Pro -2 desktops, 1 laptop
    Thread Starter

    Quote Originally Posted by Word Man View Post
    Using Win10 install media gotten either via Media Creation Tool or downloaded from TechBench, are you going to use a DVD or USB flash drive?
    Well, I created a DVD from the 1511 ISO a while ago and did a clean reinstall of Win10 on an old BIOS-only PC. I still have the DVD, but I still have the ISO file and can build a bootable USB flash memory "drive" if the DVD is only for BIOS. Is the DVD limited to BIOS?
    Quote Originally Posted by Word Man View Post
    Two main things to consider are: 1) Whether Win10 installs as MBR (for BIOS/Legacy booting) or GPT (for UEFI booting) will be determined by how you set the BIOS, i.e., if you want to go to GPT disk scheme, set the BIOS for UEFI boot and boot the Win10 install media as UEFI (Media Creation Tool will create a USB flash drive that's bootable both UEFI and legacy) and 2) To do a truly clean install, you need to select Custom Install after booting from the Win10 media and starting install and then delete all partitions on your system disk (best to have all other disks except boot device disconnected) until all space is unallocated, then Win10 will create all partitions it needs on the unallocated disk according to how you booted the install media (GPT for EUFI, MBR for legacy boot).
    I have one internal expansion drive, one external USB-attached expansion drive, and a NAS drive. Disconnecting the USB-attached drive is trivial, and I assume the NAS drive will be invisible to the installation process, but I would rather not futz around with disconnecting the internal expansion drive. Are you saying that the installation process is going to reformat it? And (assuming I have backups), do I care whether the internal expansion drive becomes a GTP drive?
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  10.    27 Apr 2016 #10
    Join Date : Aug 2015
    Penn's Woods
    Posts : 1,288
    Windows 10 Home

    Quote Originally Posted by pokeefe0001 View Post
    Well, I created a DVD from the 1511 ISO a while ago and did a clean reinstall of Win10 on an old BIOS-only PC. I still have the DVD, but I still have the ISO file and can build a bootable USB flash memory "drive" if the DVD is only for BIOS. Is the DVD limited to BIOS?
    No, the DVD should also work for UEFI. Just make sure you've set up your DVD to boot UEFI - have a look at this post by topgundcp: https://www.tenforums.com/installatio...tml#post526551 Highlighting actually shows difference between MBR boot USB and UEFI boot USB for a USB that can do either, but your DVD should show (identified in BIOS by the optical drive manuf/model, not volume label of DVD) as a selection to boot from.

    Quote Originally Posted by pokeefe0001 View Post
    I have one internal expansion drive, one external USB-attached expansion drive, and a NAS drive. Disconnecting the USB-attached drive is trivial, and I assume the NAS drive will be invisible to the installation process, but I would rather not futz around with disconnecting the internal expansion drive. Are you saying that the installation process is going to reformat it? And (assuming I have backups), do I care whether the internal expansion drive becomes a GTP drive?
    Disconnecting an internal disk is just a precaution people recommend and is more applicable when user isn't clear on which disk they are looking at during the install, particularly if they have the target drive on, say, a SATA port other than 0, then they end up surprised that a partition necessary for boot was installed on a drive different than what they expected. SO, my answer is, as long as you're paying very close attention to which disk is designated as first internal UEFI boot disk in BIOS, which disk Win10 install is presenting for you to delete partitions from and install to (pay attention to disk 0 versus 1, any volume labels you have which give you that certainty), you should be OK leaving the expansion disk hooked up.

    You certainly should care whether the expansion drive is repartitioned to GPT (GUID Partition Table) or reformatted if you have data on that disk you value that you haven't backed up. But since it's backed up, and being a data disk (not UEFI booting disk with OS) - whether that stays MBR or you also purposely convert it to GPT is strictly up to you.
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