# Starting local installations

You can start the installation of your operating system in 2 ways:

- By booting to installation media,
- By starting the installation from within a full Windows environment (DISMTools 0.6.1 and later), or
- By booting to the boot image of the installation disc file via the Preboot eXecution Environment (PXE) (DISMTools 0.7 and later)

In DISMTools 0.7.1 and later, performing these tasks has become much easier thanks to a new autorun application included in the root of the installation media:

## Starting from a full Windows environment

DISMTools 0.6.1 and later come with a program that prepares your computer for OS installation. This is called HotInstall, and the process of computer preparation is as follows:

NOTE: HotInstall does not support Ventoy drives, due to the way they work

IMPORTANT: HotInstall WILL NOT perform an upgrade. It will only prepare your computer for a clean installation of the operating system.

1. Start `setup.exe` in the root of the DVD or USB drive. If you see a notification when inserting the installation media, you can also click on it to start the installer, effectively taking advantage of AutoRun:

2. Accept the disclaimers and click Next:

3. Review that the ISO file contains the installation image you want to test, and click Next. On this screen, you can also export all your third-party drivers to a folder, in case you need them later:

4. Wait for your computer to be prepared for installation. This process will take some time, depending on your computer's performance:

After restarting your computer, choose "DISMTools Operating System Installation" (if it is not selected by default) and press Enter. The first stage of the installation will start:

## Selecting the disk and partition

The PE Helper will get the disks that are available on your computer:

On this screen, you can also stop for a moment to take actions if something does not look right with the disk listing, or if you want to see what disks have enough free space for the installation of your Windows image:

- If you don't see the disk you want to use, it could be because your computer uses a third-party disk controller. If that is the case, type `DIM` and press Enter to open the Driver Installation Module. More information on how to use this tool can be found in the External Tools section of the documentation
- (Only for installations started with HotInstall) If you want to see the free space on your disks, type `DSCR` and press Enter. This will show you the Disk Space Checker report generated by HotInstall:

After selecting the disk, you will be asked to select the partition where the operating system will be installed. You can choose to clean all the partitions of your disk, or you can choose to format a specific partition:

IMPORTANT: all actions past this point are irreversible. Make sure that you have backed up your data, and that you have selected the correct disk, before proceeding.

## Choosing the index of the Windows image

After selecting the disk and partition, you will be asked to choose the index of the Windows image that you want to apply. The PE Helper will show you basic index information, including the name you have given to the image:

You can also see more information about the image by typing `INFO` and pressing Enter:

After choosing the index, the PE Helper will apply the image to the selected disk or partition, will run serviceability tests, and will create boot files.

After everything is done, your computer will restart automatically in 10 seconds:

From this point, you can remove the installation media and let your computer finish operating system configuration.

## Serviceability tests

Serviceability tests are performed during OS installation to make sure that the image that has been applied is valid. They are only run if the architectures of the PE and the image are the same, and must pass in order to successfully complete the installation of the operating system.

Windows Setup also performs serviceability tests right before the first reboot.

If these tests fail, you may need to repair the component store of your Windows image.

## Partition table overrides

Picture this. You have 2 machines: a laptop that you've been working on to repair it and/or upgrade it; and a desktop PC on which you do all your OS deployment tasks. Both machines use different firmware types, with the desktop PC using BIOS and the laptop using UEFI without the Compatibility Support Module. The laptop is still being serviced, but you still want to deploy the operating system to it. So, you grab the laptop's internal drive and plug it into your desktop PC. That is where partition table overrides can help.

Partition table overrides allow you to configure the PE Helper to use a specific partition table scheme on a destination disk regardless of the platform you're running it on. At the partition selection screen, press `O` to configure the partition table override. You can use one of the following by selecting their respective option keys:

Partition table override | Option Key
--- | ---
MBR partition table override (for BIOS systems) | `M`
GPT partition table override (for UEFI systems) | `G`
No partition table overrides if previously set | `C`

Note that partition table overrides will only take effect if the target disk is cleaned of any existing partitions. Partition table overrides don't have any effect if you use them to deploy an operating system to the same computer you've booted the environment from.

Partition table overrides not only affect the target disk layout, but also the procedures taken to create boot files to be the most optimal for the target system's platform. After OS deployment with partition table overrides set, your computer will shut down, so you can take out that drive and put it on its target system.

## UEFI boot binary selection

During OS installation, you may be asked which UEFI boot binary you want to use. This happens when the following conditions are met:

- No partition table overrides are set,
- The target platform is UEFI,
- Secure Boot is enabled, and
- The boot file creation application, `bcdboot.exe`, contains flags to copy boot files signed with new certificates (`/bootex`)

If all conditions are met, you will be asked to choose whether you want to use boot binaries signed with Microsoft Windows Production PCA 2011, or with Windows UEFI CA 2023:

This question is asked by both the PE Helper and the WDS Helper Client.

You should know which binary to use based on whether the required certificates are present in the target system's Secure Boot database, and whether the target operating system you want to deploy comes with updated boot binaries out of the box. You will be told if you can use UEFI CA 2023 binaries with the current system, but not if the target operating system supports them.

If your computer does support UEFI CA 2023, but you are not sure whether to use them, continue with the default option by pressing ENTER, and the PE Helper will use the UEFI CA 2023 binaries, if available. If the PE Helper does not find updated boot binaries, it will fall back to using Microsoft Windows Production PCA 2011 binaries. Typically, operating system releases start supporting UEFI CA 2023 binaries after updates released on or after February 2024.

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