Microsoft's Windows To Go is not longer available in Windows 10, version 2004 and later. Now, there are some unofficial software, such as iSumsoft SYSOnUSB. They can help install portable Windows 7/8/10/11 OS on an external hard drive or USB flash drive. Then, you can boot and run the Windows directly from the external drive without having to install it again.

1. Connect the external hard drive to the software.
2. Add the Windows ISO file to the software.
3. Select the Windows version you want to install on the external drive.
4. Start installing Windows on the external drive.

In this way, you can install a fresh Windows OS on your external hard drive. When you first boot from this drive, it will require you to take a few minutes to complete the Windows initialization setup to get to the Windows desktop, just like when you turn on a brand-new computer for the first time.

Microsoft's Windows To Go is no longer available in Windows 10, version 2004 and later. Now, there are some unofficial software, such as iSumsoft SYSOnUSB. They can help install portable Windows 7/8/10/11 OS on an external hard drive or USB flash drive. Then, you can boot and run the Windows directly from the external drive without having to install it again.

1. Connect the external hard drive to the software.
2. Add the Windows ISO file to the software.
3. Select the Windows version you want to install on the external drive.
4. Start installing Windows on the external drive.

In this way, you can install a fresh Windows OS on your external hard drive. When you first boot from this drive, it will require you to take a few minutes to complete the Windows initialization setup to get to the Windows desktop, just like when you turn on a brand-new computer for the first time.