Now I found an article practically saying the Windows loader should be back upon deleting Linux partition, so I want to make sure: I know from past the major problem was when I removed Ubuntu, I either still got into the GRUB booting menu, or I couldn't boot at all, and had to format HDD and start over. In the book Mastering Malware Analysis: The complete malware analyst's guide to combating malicious software, APT, cybercrime, and IoT attacks, there're 2 sections in chapter 2 called "Process loading step by step" and "PE file loading step by step" which document how the Windows PE loader is loaded and how it works. If we're really strict about it, we might say that the first part of the loader is PspAllocateProcess, since that's what allocates the initial structures. However, the kernel part of the loader begins when ntdll!NtCreateUserProcess transitions into kernel-mode. The instant you call CreateProcess, you're technically running the loader. The tricky part with your question is that the "loader" isn't really something that gets control flow. running a process under an alternative security context. There are different APIs for doing different things, e.g. The PE loader is exposed by a set of user APIs in kernel32.dll, under the CreateProcess family. When and where is the control flow exactly transferred to the loader? The PE format is well documented but there seems to be a little info regarding the functioning of the loader itself. I have read that the PE loader is responsible for loading executable images from disk. So, the question is is there any way to install a boot loader to my new system disk without wiping it? I'm guessing the installation starts at the first sector, and blocks the ability to use boot sect (I've tried, and it fails saying it can't install on this disk). I'm guessing this is why the installer never created a boot loader partition on my new disk automatically.As long as my old system disk is running, I'm able to boot into my new installation (I get two options in the boot loader menu), but now it's failing more and more, and I need two or three reboots in order to even get to the boot loader menu. When I then installed Windows 7 on the new disk, I was planning on keeping the faulty disk as it was still spinning, but forgot to disconnect it during the new installation. The system disk was starting to present some disturbing errors and mystical freeze lags, so I decided to get a new disk to serve as the system disk. I have a Windows 7 installation that doesn't have a boot loader on the disk.Basically, the story goes I had two disks on my PC where one of them served as the system disk with Windows 7 installed, and then a storage disk. Once it's done, you can verify the new bootloader was written by running dir N:\EFI, where you should see a Microsoft directory containing the new Windows Boot Manager as well as a boot directory containing the fallback bootloader (along with other directories for any other bootloaders you have installed, such as GRUB for Linux). This command rebuilds a new UEFI-compatible bootloader on the ESP mounted at N: using the Windows installation mounted at C:\windows. Also note that the following steps should not affect an EFI GRUB install as long as you do not otherwise delete GRUB's existing directory on the ESP.įinally, write the new bootloader to the partition with bcdboot C:\windows /s N: /f UEFI. Especially do not do this if you have a Linux distro on another partition or else you'll have to reinstall GRUB as well once you're done with this. This is probably not necessary under normal circumstances, however, as bcdboot seems to do a good job of cleaning things up itself. (Optional) If you are not currently dual booting and want to fully clean the ESP before writing a new bootloader, run format N: /FS:FAT32 to reformat it as FAT32. There's unfortunately almost no up-to-date guides on fixing the UEFI Windows Boot Manager (almost all of them just say to run the graphical Startup Repair utility, but that doesn't fix the problem in all cases), but I finally found the correct solution buried in this article, which requires the use of the bcdboot command instead: The other answers given here work great on MBR/BIOS systems, however if you're on a UEFI system like I am, bootsect will just write a semi-functional boot MBR over the GPT protective MBR and bootrec just gives an "Access denied" error message, and neither one has a functional option to fix a broken EFI system partition, which on a UEFI/GPT drive is what contains the bootloader that used to be stored in the MBR.
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