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Windows 7: How to properly remove Win7, in a dual boot config

31 Jan 2015   #11
Microsoft MVP

Vista, Windows7, Mint Mate, Zorin, Windows 8

Greg is right. It is not optimal because you get a small performance hit for the boot time. We are probably talking 5 seconds or so. What Greg suggests will work if there are no Gremlins on the way.

My System SpecsSystem Spec
31 Jan 2015   #12
Microsoft MVP


I was thinking more about drive failure or a even a BIOS setting change that removed the System Reserved drive from booting first. Windows 8 would stop booting for a reason that could have been prevented.

It could never really be proper (the title of OP's thread) to have it booted from another hard drive that only has the System partition on it.
My System SpecsSystem Spec
31 Jan 2015   #13
Computer Guru


If I could chime in with my two cents here, pretty much all the approaches in this thread are correct and will wind up with a setup wherein the Windows 7 partition can be deleted and the Windows 8 partition will boot.

However, for the sake of perfection and without doing more steps than you need to, here's what you would need to do to have a configuration where the entire *disk* that contains Windows 7 now will no longer be used, and the PC will boot from the physical disk that has Windows 8 installed:
  1. Run EasyBCD from either Windows 7 or Windows 8, and use the Change Boot Drive feature, as explained in WHS' excellent and to-the-point tutorial, selecting the Windows 8 partition as the new boot drive.
  2. Once that's done, go in the BIOS and change the order of boot drives from the disk containing Windows 7 to the disk containing Windows 8.
  3. OPTIONAL: Once you're back in Windows 8, run EasyBCD to remove the now-defunct Windows 7 entry.

That's it. Now you're free to remove the Windows 7 disk or do whatever you see fit with it. Neither the Windows 7 partition nor the boot partition on that drive will be in use. If it doesn't boot after changing the drive in the BIOS, follow the earlier advice and run startup repair.

Some random info:
  • Windows 8 does not necessarily mean UEFI. Windows 7 (64-bit edition) and Windows 8 both support UEFI, but they'll only use UEFI if the PC supports UEFI and the disk you've selected to install Windows 8 to is formatted in GPT, not MBR.
  • Normally, all OSes on the same PC will boot the same way (either MBR-only or GPT/EFI-only). The exception to this is where you have multiple hard disks, you have the option of setting them up to boot one in legacy mode and one in UEFI mode if the BIOS is configured to allow both - but that never happens by default so we can ignore that case.
  • On BIOS/MBR installations, you do not need a separate boot partition at all. The Windows partition can be the boot partition and the system partition. In the above "solution" configuration, that's what we end up with.
  • EFI, on the other hand, requires a minimum of 3 partitions: the MSR (a reserved partition without a filesystem that contains absolutely nothing, but Microsoft requires it anyway), the FAT EFI boot partition (which will contain BOOTMGR and the EFI BCD), and the Windows system partition (which will likely be NTFS). You can get away with only two partitions if Windows is installed to the EFI boot partition, meaning Windows will be installed to a FAT32 partition - basically, never.
  • With SATA, there's really no more concept of disk 0, disk 1, etc. which is really an IDE/ATA thing. The boot device the BIOS picks isn't the first disk, it's just a disk. So don't feel that a particular disk must be the boot disk, just pick whatever works.
  • Having a partition from a different disk be the boot partition won't actually slow anything up (besides maximum ~250 milliseconds of seek time, if that), but it's rather inconvenient as your PC is now reliant on two disks to be working correctly (and unchanged) in order to boot. Minimize complexity and keep it one is the way to go.

Now as for EasyBCD, when you use the "change boot drive" feature, all the following is taken care of (as documented here):
  • Install the BOOTMGR bootloader to the selected partition
  • Make the selected partition active
  • Install the bootloader to both the bootsector and the MBR of the selected partition
  • Copy all entries from the old boot partition to the newly-selected one
  • Update partition references to work with the new boot partition

It doesn't actually *move* anything, but it does copy everything. If the new boot destination is on the same disk, the partition that used to be active will no longer be active, as there can only be one active partition at a time; thus the PC will automatically boot from the new boot partition.

However, on a PC with multiple disks, each disk can (and does) have its own active partition. Setting the active partition on one disk won't affect the other, and the BIOS will continue to attempt to boot from the same disk it did before - which will still contain an active partition, and cause the PC to load from there.

So you need to go into the BIOS and tell it the new boot disk is the one that has the newly-minted boot partition.

I hope that clears things up! We literally just published an article that we've dubbed "everything you wanted to know about how your PC boots up, part one" that I personally feel is a must-read as it covers everything from the BIOS to the disks and partitions to the bootloader to the OS. Part two is under works, and will cover the same thing only for UEFI and GPT.
My System SpecsSystem Spec


 How to properly remove Win7, in a dual boot config

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