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I have Windows 10 / Windows 7 dual boot on my laptop. Boot mode is UEFI with CSM and my hard drive is correctly formatted and partitioned in GPT. Windows 7 used to work well before I decided to fully re-install it.

First bit of background, (I believe) I am experienced in installing Windows and playing around with WIMs and related utilities. I manually captured a backup WIM a long time ago but now I don't want to use it. I took install.wim from the 64-bit Windows 7 DVD image and applied it by hand:

Dism.exe /Apply-Image /ImageFile:E:\sources\install.wim /Index:3 /ApplyDir:G:\ /Verify

I formatted drive G prior to installing so it's clean.

I left the BCD unchanged and tried booting it. Well it stuck at disk.sys. I then applied the backup WIM to make sure everything is fine. So it is. The system from my backup WIM functions normally, without anything else changed. This ensures that all my configuration like BCD and BIOS settings are correct.

I do NOT want to create any USB installer or burn a DVD. How would I make a freshly "installed" Windows 7 boot?

  • UEFI with CSM == “BIOS”. Windows only supports booting from GPT in “real” UEFI mode. So which is it that you want? What do you mean by “left the BCD unchanged”? Where does it come from? – Daniel B Jan 8 '18 at 9:48
  • @DanielB BCD unchanged = left at previous state where my backup image boots perfectly. The previous state is exactly a Windows 7 64-bit on a GPT booting in UEFI/CSM. Note as well that the ESP is on the same drive. – iBug Jan 8 '18 at 10:16
  • For Windows, GPT => UEFI. Please stop using wrong terminology in order to avoid unnecessary confusion. It's UEFI mode, period. You can also disable CSM once and for all. – user772515 Jan 8 '18 at 11:56
  • @MichaelBay There are three options in my MB settings: BIOS, UEFI with CSM, UEFI. What do you mean? AFAIK Windows 7 won't boot without CSM. – iBug Jan 8 '18 at 14:22
  • "BIOS" (Legacy) is one mode, "UEFI" is another mode, "UEFI with CSM" is NOT a third one, it merely allows dual or multi-booting OSes in either UEFI or Legacy mode. Windows 7 CAN be installed in UEFI mode and if it is installed in a GPT drive it certainly is (Windows only supports booting from GPT in “real” UEFI mode). CSM, the "thing" that emulates the 40yo BIOS, is NOT required if all the OSes are installed in UEFI mode. Rule of thumb: Always use UEFI mode and that mode only unless the OS has no support for it, not the case here. – user772515 Jan 8 '18 at 14:31
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Your assumption is incorrect that the unchanged BCD settings can be used for the new install. You need to generate new settings with either the bcdboot or bootrec command-line utilities after you've applied the image.

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