Hello,
Thank you for posting in Microsoft Community forum.
Based on the description, I understand your question is related to uninstall windows server.
Uninstalling Windows Server:
Ensure you have backed up all important data and configurations. Download the Windows Server ISO file and create a bootable USB drive. Insert the bootable USB drive and restart your server. Enter the BIOS/UEFI settings and set the USB drive as the primary boot device. During the installation process, you’ll be prompted to select a partition. Delete all existing partitions to remove the current Windows Server installation. Confirm the deletion of partitions. This will erase all data on the server.
Reinstalling Windows Server
Follow the on-screen instructions to install Windows Server on the unallocated space. Set up your preferred language, time, and keyboard settings. Enter your Windows Server product key when prompted. Choose “Custom: Install Windows only (advanced)”. Create a new partition on the unallocated space and select it for installation. Follow the remaining prompts to complete the installation. The server will restart several times during this process.
After installation, configure the server settings, such as the administrator account and network settings.
Reinstall Windows - Microsoft Support
Have a nice day.
Best Regards,
Molly