# Why Is Sysprep Required for Creating a Private Image from a Windows ECS?

#### Why Is Sysprep Required?

For a user that needs to be added to a domain and uses the domain account to log in to Windows, Sysprep is required before a private image is created. Otherwise, the image will contain information about the original ECS, especially the SID. ECSs with the same SID cannot be added to a domain. If Windows does not require any user or ECS to be added to a domain, you do not need to run Sysprep.

- Before running Sysprep, ensure that Windows is activated.
- For details about Sysprep, visit https://docs.microsoft.com/en-us/previous-versions/windows/it-pro/windows-vista/cc721940(v=ws.10)?redirectedfrom=MSDN.

#### Restrictions on Running Sysprep

Sysprep can only be used for configuring a new Windows installation. You can run Sysprep multiple times to install and configure Windows. However, you can reset and activate a Windows OS only three times, and you are not allowed to use Sysprep to re-configure an existing Windows OS.

In the Windows command line, enter the following command to check how many times you can run Sysprep in the displayed Windows Script Host dialog box:

slmgr /dlv

If the value of Remaining Windows rearm count is 0, you cannot run Sysprep.

Parent topic: Image Creation