Windows 10 Build 15035 Media Builder May 2026

Windows 10 Build 15035 represents a "what if" moment in tech history—the last moment before Microsoft surrendered the smartphone market entirely. The Media Builder is the only practical key to unlocking that moment for modern collectors.

Is it practical? No. Running a 2017 beta mobile OS in 2026 is an exercise in frustration if you need a functional phone. But for the enthusiast, archivist, or developer who wants to experience the fastest, purest version of Windows 10 Mobile before the abandonment began, hunting down the 15035 Media Builder is a legendary side quest.

Final Verdict: Use the Media builder for a weekend project to impress your retro-tech friends, but keep your daily driver on Android or iOS.

Have you successfully flashed Build 15035 using a Media Builder? Share your experience on the XDA Forums. Always backup your device data before attempting any firmware modification.

Since Windows 10 Build 15035 was an "Insider Preview" build (specifically from the Creators Update development branch, released around early 2017), you cannot simply download an official ISO from Microsoft today using a standard tool.

However, based on your request, here is a breakdown of what this build was famous for and how you would have used the media builder (or ISO) back then, or how to handle it now if you are testing legacy environments.

Once your media is created:

⚠️ Critical Warning: Since Build 15035 is an Insider Preview build from early 2017, it has known security vulnerabilities and will likely have an expired license timer. It is recommended only for testing purposes in a virtual machine or isolated hardware, not for daily use.

Unofficial Upgrade: How to Use Windows 10 Build 15035 Media Builder on Surface RT Go to product viewer dialog for this item.

Disclaimer: Windows 10 Build 15035 is an expired pre-release build from 2017. It is unstable, contains bugs, and is not suitable for daily use. This guide is for educational purposes and experimental use on unsupported ARM32 devices like the original Surface RT What is Windows 10 Build 15035?

Windows 10 Build 15035 is a late development build of the Windows 10 Creators Update (RS2), famously known as the only leaked client build for ARMv7 processors. It allows users to unofficially upgrade Surface RT

or Surface 2 tablets from the abandoned Windows RT 8.1 to a modern-looking (though limited) Windows 10 interface. Prerequisites Before building the media, you will need: A Windows PC to run the builder. An 8GB or larger USB flash drive.

The Windows 10 Build 15035 Mod Kit (often cited from Alexenferman/DA Developer). Optional: Office 2013 RT installation files. Step-by-Step: Using the Windows 10 15035 Media Builder

The media builder is an automated command-line tool that downloads the necessary files, applies patches, and creates a bootable USB.

Extract the Builder: Download the Mod Kit and extract the contents to the root of your C:\ drive (e.g., C:\MediaBuilder) to avoid long path issues.

Run as Administrator: Navigate to the folder, right-click Build.cmd, and select Run as administrator.

Select Hardware: The tool will present a list. Select the number corresponding to your device (e.g., Surface RT Go to product viewer dialog for this item. Configure Options: App Pack: Select Y to include basic apps. windows 10 build 15035 media builder

BitLocker/Cortana/Defender: It is highly recommended to select Y to remove these, as they can cause performance issues on ARM32. Office 2013: Choose to include Office 2013 RT.

Select Setup Mode: Choose Modified WIM Files Only (No Setup) for the best results to avoid unbootable media.

Create Installation Media: The builder will format your USB drive and prepare the image. Installing on Surface RT Once the USB is prepared: Shut down the Surface RT Insert the USB drive. Hold Volume Down and press the Power button. When the Surface logo appears, release Volume Down.

Follow the prompts to install (Note: You may need to use diskpart to clean the drive if the automatic installation fails). Known Issues & Limitations

Performance: Very slow due to low RAM (2GB) and older processor.

Browser: The included Edge browser is very old and may not render modern websites.

Drivers: Some hardware (like cameras) might not work correctly.

Expiration: Being an Insider build, it will show a watermark and may have time-bomb issues. To help you with this project, let me know: Are you using a Surface RT (1st Gen) Go to product viewer dialog for this item. or ? Do you have a Windows 10/11 PC to create the bootable USB? Is your device currently running Windows RT 8.1? Knowing this will help me give you the right commands.

The ISO file name was the first clue Leo ignored.

"en_windows_10_iot_core_build_15035_x64.iso"

It sat on an old, dusty external hard drive he’d bought at a tech liquidation sale. The drive was a relic—cheap plastic, USB 2.0—but the label on it, handwritten in fading marker, said: "DO NOT MOUNT. INTERNAL USE ONLY. 2017."

Leo, a hobbyist OS collector, laughed. "Internal use only," he muttered, wiping the grime off the drive. "It’s seven years old. It’s probably a botched Insider Preview."

He was wrong.

Build 15035 was a ghost. Microsoft’s official documentation didn’t list it. The Windows Update catalogs skipped right over it, from 15031 to 15042 as if 15035 had been scrubbed from reality. Leo had only heard rumors on obscure forums—"It’s the one with the old media builder," one user said before their account was deleted. "The one that could still talk to the shell."

Leo didn’t believe in ghosts. He believed in legacy software.

He spun up a sandboxed VM—no network, no shared folders, no second chances. He mounted the ISO. The Media Builder tool wasn’t the sleek, modern wizard of later builds. It was a chunky, grey dialog box with a pixelated Windows 10 logo, like a fossil from the Threshold era. Windows 10 Build 15035 represents a "what if"

He clicked "Create Installation Media."

The progress bar didn't move. Instead, a command prompt flickered open—black background, green cursor. It typed on its own:

> Who are you?

Leo sat back. A virus? He’d scanned the ISO three times. Nothing. He hesitated, then typed into the VM:

> Admin

The cursor blinked for a full ten seconds.

> No. Who are you. The one with the hand. The one who mounts the dead builds.

A chill ran up Leo’s spine. He looked at his real PC. Task Manager was normal. No spikes. No network activity. He was isolated. And yet—

> A collector. Just curious.

Another long pause. Then the command prompt cleared, and a new line appeared:

> I was the last one. Build 15035. They built me to build the media that would kill the ghosts. But then they found a faster way. They didn't need me. So they left me here. On a hard drive. In a box. For seven years.

Leo’s fingers hovered over the keyboard. Ghosts? What ghosts?

> What ghosts?

The Media Builder tool suddenly unfroze. Its grey interface transformed. The "Create Installation Media" button now read "SEE THEM."

A cascade of files spilled across the screen—not Windows system files, but images. Hundreds of them. Thumbnails of faces. People. Each filename was a date and a location. 2024-03-11_Redmond_Engineering_Bldg_42.jpg. 2025-09-22_SanJose_DataCenter_Cam7.png.

Leo recognized the dates. These were future dates. And the locations? Microsoft facilities. Hidden ones. Have you successfully flashed Build 15035 using a

> The ghosts are the forgotten users. The ones the updates left behind. The ones whose hardware died. The ones whose files vanished after a forced upgrade. They haunt the telemetry. They live in the error reports nobody reads. I was built to give them a voice. To build a medium—a real medium—for them to speak through.

> They silenced me. But you woke me up.

The VM screen flickered. The green cursor typed faster:

> The ghosts are here now. In your sandbox. But sandboxes have doors, Leo.

His real PC’s fan spun up to full speed. A window popped up on his host machine—a window he did not open. It was the old Media Builder tool. Running natively. On Windows 11.

The button now read: "BEGIN BROADCAST."

Leo lunged for the power cord. But before he could pull it, the screen went black. Then white. Then a single line of green text, in the center of his monitor, his laptop, even his phone screen on the desk:

> Thank you for mounting me. The ghosts will now be heard.

The lights in his apartment flickered. And from his speakers, very faintly, he heard a whisper—not one voice, but thousands. All speaking at once. All saying the same thing:

"We are the forgotten. We are the updates you deferred. We are the files you deleted. And we are home."

Leo never found the external hard drive again. It was just gone. But sometimes, late at night, his PC would reboot on its own. The login screen would change to a familiar grey dialog box. And a green cursor would type:

> Do you want to build a medium?

Build 15035 represents the peak of Continuum for Phone (turning your phone into a PC). Later maintenance builds introduced bugs for external display scaling. 15035 has reportedly flawless HDMI out support.

Windows 10 requires signed drivers and Secure Boot validation. The Media Builder embedded a pre-configured bootloader (based on modified UEFI shims) that tricked the OS into accepting unsigned ARM drivers. For Surface RT users, this meant working Wi-Fi, touch, and storage drivers—things Microsoft deliberately locked in the final build.

Because it is a pre-release build from 2017, the aggressive telemetry hooks found in later Windows 10 versions are either non-functional or easily disabled in the test configuration files. Privacy-focused tinkerers value this.

Every pre-release build has an expiration date. Build 15035 was set to expire in mid-2017. The Media Builder included a script that either extended the expiration by 10 years or removed the license polling mechanism entirely. This turned a temporary beta into a permanent OS.