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description: "VHD_Tool++ is a specialized utility for IODD devices to create and manage virtual hard disk (VHD/RMD) files. Learn how to create a bootable virtual USB thumb drive using VHD Tool and Rufus for OS installation, Windows-To-Go, and low-level system utilities."
---

# IODD VHD Tool++ & Virtual USB Drive Guide

This directory contains **VHD_Tool++** and related guides for managing virtual disk images on IODD devices.

VHD (Virtual Hard Disk) files act as physical hard drives. By utilizing VHD/RMD files, your IODD device can emulate a bootable USB thumb drive, which is especially useful for motherboards that do not support booting from a USB DVD-ROM.

## 🚀 Key Features & Use Cases
*   **Create USB Installation Media**: Easily boot from ISOs (Windows, Linux, UEFI).
*   **Windows-To-Go (WTG)**: Run a full operating system directly from your IODD.
*   **System Maintenance**: Flash BIOS, run DOS firmware, or use low-level utilities on systems without an installed OS.

## 🛠️ How to Create a Bootable Virtual USB Drive

### STEP 1: Make a VHD File using VHD_Tool++
1. Connect your iODD to your PC and run **VHD_Tool++**.
2. Check the `Largest linear space` to determine the maximum size of the VHD you can create. *(Note: The VHD file must be larger than your ISO file).*
3. Create the VHD file directly on the iODD's HDD.
4. **For 2531 / 2541 models only**: Change the file extension from `*.VHD` to `*.RMD`. (On these specific models, VHD is recognized as a fixed HDD, while RMD is recognized as a removable thumb drive).
   *(Note: For ST300, ST400, MINI, and MINI PRO models, simply use the `*.VHD` extension and set the Removable/Fixed drive option via the device's internal menu).*
5. Mount the `*.VHD` (or `*.RMD`) file on your IODD device and format it (FAT32, exFAT, or NTFS).

### STEP 2: Make it Bootable using Rufus
1. Download and run **Rufus**.
2. Select the mounted IODD virtual drive in Rufus.
3. Choose your Bootable ISO file.
4. Click **Start** to create the bootable drive. *(Caution: Existing data on the VHD/RMD will be formatted and deleted).*

## ⚠️ Important Warnings
If you are using the virtual drive as an operating system (e.g., Windows-To-Go) in **DUAL-MODE** with the real drive **Write-Enabled**, you must strictly follow these rules to prevent fatal data corruption:
1. **DO NOT** defrag the real drive (iODD main drive).
2. **DO NOT** move the `*.VHD` or `*.RMD` file that is currently in use.
3. **MUST DISABLE** any automatic defrag services on the host OS.

## 💡 Pro Tips
*   **LUN Modes (For 2531 / 2541 ONLY)**: You can change the device mode by renaming the file.
    *   `IODD.RMD` : CD-MODE (Default)
    *   `IODD&D.RMD` : DUAL-MODE
    *   `IODD&DW.RMD` : DUAL-MODE, Real HDD is writable
*   **Unmount Shortcut**: Press and hold the `7` key (for 2541) or the `down` key (for 2531) for 3 seconds to unmount all RMD/VHD files.
*   **Compatibility**: iODD only supports **fixed VHD** files. Dynamic VHD or VHDx files are not supported.
*   
For more detailed information, please refer to your product's Quick Guide or visit the official help page: [VHD Tool++ Help](https://help.iodd.kr/product-reference-wiki/vhd-tool-plus-plus)