tetoOS (Windows) Install Tutorial

Important: Pre-Installation Checklist

Please read and perform these critical steps before starting any part of the installation process:

Check Boot Mode (UEFI vs Legacy BIOS): Press Win + R, type msinfo32, and press Enter. Look for BIOS Mode in System Summary:
- If it says UEFI → Choose GPT partition style.
- If it says Legacy → Choose MBR partition style.
Clean PC Check: Ensure your PC is completely free from malware or viruses. If you suspect an infection or are unsure, do not install from within the compromised system. Instead, create a bootable USB drive using another clean, trusted computer.
Disable Security Software: Temporarily disable Windows Defender or any third-party antivirus software while preparing installation files and partition tools, as security software often flags and blocks OS reinstall utilities.
Rename Drive C to "Install Here": Open File Explorer, right-click Drive C, and rename it to Install Here. This is extremely important so you can easily distinguish it and avoid accidentally formatting or wiping the wrong drive during installation.

1. Choose Installation Method

Select one of the three installation media preparation methods below to expand its step-by-step tutorial:

Recommended Method 1: Ventoy (USB Flash Drive) ▼

First, download the tetoOS ISO file from the Download button, then prepare your bootable USB flash drive using Ventoy (Ventoy Download).

Step-by-Step with Ventoy

1. Select your USB drive: Download Ventoy from official website, extract it, and run Ventoy2Disk.exe. Make sure the target USB drive selected in the Device dropdown is correct.

Ventoy2Disk Device Selection — Select your flash drive in the Device list

2. Partition Style & Secure Boot: Click the Option menu at the top. Under Partition Style, choose GPT or MBR according to the boot mode you determined earlier. You can also toggle Secure Boot Support if needed.

Ventoy Partition Style and Secure Boot Option — Configure Partition Style (Option menu) and Secure Boot Support

3. Click Install: Click the Install button. A warning prompt will show informing that your USB drive will be formatted and all data erased. Click Yes to confirm.

Ventoy Format Warning Confirmation — Confirm the warning prompt to proceed with formatting

4. Copy ISO into Ventoy: Simply copy and paste the tetoOS .iso file directly into the Ventoy partition. You do not need to extract or re-format anything.

Copy ISO to Ventoy Drive — Copy and paste the ISO file directly into the flash drive

5. Boot into Ventoy: Restart your PC and press your boot menu key (F12, F11, F8, or Esc depending on your motherboard). Select your USB drive, and the Ventoy boot screen will show your ISO list. Select tetoOS to start booting.

Ventoy Boot Menu Screen — Ventoy boot menu screen

Alternative Method 2: Rufus (USB Flash Drive) ▼

Using Rufus?
Use version 3.16 (Rufus Older Versions Download). Do not use the latest Rufus: its newer options made for original Windows will conflict with tetoOS and cause the installation to fail.

Rufus Settings — Rufus settings: Device, Boot selection, Partition scheme, and Target system

Device: Select your USB flash drive.
Boot selection: Click SELECT and browse to your downloaded tetoOS .iso file.
Image option: Select Standard Windows Installation.
Partition scheme: In the dropdown, select GPT or MBR according to the boot mode you determined earlier (the Target system will configure automatically).
Click START and confirm the warning to write the bootable image.

No Flash Drive Method 3: EasyBCD (Direct Hard Drive Partition) ▼

We suggest buying a flash drive and follow the USB method first, it makes installation much easier. If you really can't, you can create a bootable partition on your own HDD/SSD instead using Disk Management and EasyBCD.

Preparation: Make sure you have downloaded the tetoOS ISO file, and installed the free version of EasyBCD.

Part 1: Creating the Bootable Partition in Disk Management

1. Open Disk Management: Press Win + R on your keyboard to open the Run dialog, type diskmgmt.msc, and click OK (or press Enter).

Run diskmgmt.msc — Type diskmgmt.msc in Run dialog and click OK

2. Shrink Volume: In the Disk Management window, find your system drive (Drive C:), right-click on it, and select Shrink Volume... from the context menu.

Right-click Drive C and select Shrink Volume

3. Specify Shrink Size (10 GB): In the "Enter the amount of space to shrink in MB" box, type 10000 (around 10 GB), then click the Shrink button at the bottom.

4. Create New Simple Volume: You will now see an "Unallocated" space created (around ~9.77 GB). Right-click on this black unallocated bar, and select New Simple Volume....

Right-click Unallocated space and select New Simple Volume

5. Specify Volume Size: In the wizard window, leave the "Simple volume size in MB" at its maximum default value, then click Next >.

Leave size at maximum and click Next — Keep default maximum volume size and click Next

6. Assign Drive Letter: Select "Assign the following drive letter" (e.g. drive E: or any available letter), then click Next >.

7. Format & Label the Partition: Select "Format this volume with the following settings". Set File system to NTFS, and in Volume label, type Bootable TetoOS. Ensure "Perform a quick format" is checked, then click Next > and finish the wizard.

Format partition with NTFS and label Bootable TetoOS — Format partition with NTFS and set label to Bootable TetoOS

Part 2: Copying ISO Files into the Bootable Partition

8. Mount ISO and Copy All Files: In File Explorer, right-click your downloaded tetoOS ISO file and select Mount. Open the mounted virtual DVD drive, select all files and folders inside (such as boot, efi, sources, bootmgr, etc.), copy them, and paste them into your newly created Bootable TetoOS partition. Wait until copying completes.

Right-click ISO and select Mount — Right-click tetoOS ISO and click Mount

Copy all ISO contents to Bootable TetoOS partition — Copy and paste all files from mounted ISO to Bootable TetoOS

Part 3: Registering Bootloader with EasyBCD

9. Open EasyBCD & Click "Add New Entry": Launch the EasyBCD application from your Desktop or Start menu. In the left toolbox sidebar, click on the Add New Entry button.

Open EasyBCD and click Add New Entry — In EasyBCD toolbox, click Add New Entry

10. Go to WinPE Tab & Set Name: In the lower section under Portable/External Media, click on the WinPE tab. Ensure Type is set to WIM Image (Ramdisk), and in the Name field, type Bootable TetoOS.

Select WinPE tab and name it Bootable TetoOS — Select WinPE tab, set Type to WIM Image, and Name to Bootable TetoOS

11. Browse and Select boot.wim: In the Path field, click the browse folder icon on the right. Navigate to your Bootable TetoOS drive → open the sources folder → select the boot.wim file, and click Open.

Browse to sources folder and select boot.wim — Browse into Bootable TetoOS > sources folder and choose boot.wim

12. Click Add Entry (+): With the path set (e.g. E:\sources\boot.wim), click the green plus button (+) next to the browse icon to register the bootloader entry.

Click Add Entry button in EasyBCD — Click the green (+) icon to add the entry to Windows bootloader

13. Restart and Select Bootable TetoOS: Restart your computer. During startup, the Windows Boot Manager screen will appear (either the modern blue menu or classic black menu). Select Bootable TetoOS (using arrow keys or mouse) and press Enter to boot into the installer!

Modern Blue Boot Manager Screen — Modern Blue Boot Menu: Click or select Bootable TetoOS

Classic Black Boot Manager Screen — Classic Black Boot Menu: Use arrow keys and Enter

2. Booting the Installer

Restart your computer and boot from the bootable media. You will see the "welcome to tetoOS installation" screen with several action choices:

Action	What it does
Install now	Starts the tetoOS installation right away. Click this to proceed!
View the release notes	Shows the release notes and changes of this OS version.
Explore and see your files	Opens a mini file explorer in case you need to copy or back up data quickly.
Manage disk partitions	Opens partition management to create, format or delete partitions.
Use command prompt	Opens CMD for advanced troubleshooting or diskpart commands.

3. OS Variant & Setup Options

After clicking Install now, select the tetoOS edition you want to install from the list (e.g. Windows 11 Professional). You can also check the Install Microsoft Office box if you want Office pre-installed, select your installation language, and click Next.

Select Operating System Edition — Select your desired OS Edition and click Next

Advanced Option Advanced Bootloader Configuration (WinNTSetup) ▼

Tip: If you need custom bootloader configuration or want to avoid modifying your existing EFI partition, hold Shift on your keyboard while clicking Next in the OS selection menu. This launches WinNTSetup for granular partition and boot targeting.

WinNTSetup Step-by-Step:

WinNTSetup Interface — Step 1: Check Windows installation files & Boot drive

1. Verify Installation Files & Boot Drive:
In the first section, ensure the path to install.wim / install.esd points to the source image. Below it, verify the boot drive location (EFI system partition). WinNTSetup displays green indicators for compatibility.

WinNTSetup Partition Selection — Step 2: Select the target installation drive

2. Select Target Drive Partition:
Under "Select the location of the installation drive", click Search... and carefully choose your target Windows partition (look for the partition labeled Install Here). This protects your other partitions, such as Linux root or swap.

WinNTSetup Setup Button — Step 3: Click the Setup button to proceed

3. Click Setup to Begin:
Once both the boot drive and installation drive are selected, click the "F" button to the right of the installation drive field to format the partition. Then, click the Setup button at the bottom right. In the confirmation dialog that pops up, leave the default boot options checked and click OK to start extracting Windows.

4. Disk Selection

In standard installation mode, the "Where do you want to install Windows?" window will show your disks and partitions. Select the primary partition for tetoOS (you will easily recognize it by the Install Here label we assigned earlier), format or delete partitions if needed, and click Next.

Be careful:
Formatting erases everything on that partition. Double-check the partition you pick and back up your important data first.

5. Feature Selection

While Windows files are getting prepared for installation, a custom tetoOS configuration window will appear. Here you can customize your installation preferences before ever landing on the desktop:

tetoOS Feature and Tweaks Selection — tetoOS Feature & Tweaks selection window

Group	What you can set
`Time zone`	Set your local time zone and toggle daylight saving time.
`User & Computer`	Fill in your Display name, User name, PC name, and Workgroup.
`Activate`	Tick boxes to automatically activate Windows and Microsoft Office.
`System settings`	Pause Windows Update until 2077 (ticked by default), and options to disable Windows Defender, Firewall, UAC and Hibernate.
`Tweaks, patches, etc.`	Essential tools and tweaks: 7-Zip, Registry Tweaks, Visual C++, HEIC/HEVC Codecs, and Windows 7 Start Menu / File Explorer style.

After configuring all options to your liking, click the Apply button at the bottom right corner.

For expert technician or repair shop: you can customize the feature menu by yourself. Learn more...

6. Finishing Up

Once you click Apply, the installer resumes copying files and applying your customized tweaks.

Installing Windows progress screen — Windows Setup: Getting files ready for installation

Do not force turn off your computer:
The process may take several minutes depending on your storage speed and selected tweaks.

Your computer will restart automatically several times. Once you arrive at the tetoOS Desktop, the installation is complete! You can now install device-specific drivers and enjoy your lightweight OS.