Windows Server cannot be installed

What this article covers

This article describes how to fix the error that prevents Windows Server installation when the partition style of the target disk does not match the boot mode of the server. The instructions apply to Windows Server 2016, 2019, 2022, and 2025.

The error

During Windows Server installation, the installer shows one of these messages on the disk selection screen:

Windows cannot be installed to this disk. The selected disk has an MBR partition table. On EFI systems, Windows can only be installed to GPT disks.

or

Windows cannot be installed to this disk. The selected disk is of the GPT partition style.

Why this happens

Windows requires a specific partition table depending on how the server boots:

• UEFI boot mode requires a GPT disk.
• Legacy boot mode is typically used with MBR disks.

The disk may already use a partition style that does not match the current boot mode, which blocks the installation. For disks larger than 2 TB, GPT is the only practical option, since MBR cannot address the full capacity.

How to check the current boot mode

To see whether the installer is running in UEFI or Legacy mode, press Shift + F10 on the disk selection screen to open the command prompt, then run:

msinfo32

In the System Summary, look at the BIOS Mode value. It shows either UEFI or Legacy.

Two ways to fix it

There are two ways to resolve the conflict:

• Change the boot mode in the server BIOS to match the existing partition style. This keeps the data on the disk.
• Convert the partition table on the disk to match the boot mode. This wipes the disk completely.

The first option is recommended if the disk contains data that must be preserved. The second option is suitable for clean deployments but completely erases the disk.

Option 1: Change the boot mode in BIOS

This is the recommended option when you are not sure what is on the disk or want to keep its contents.

Restart the server and enter the BIOS setup. On INTROSERV dedicated servers this is done through IP-KVM. The exact key to enter the BIOS depends on the hardware vendor (commonly Delete, F2, F11, or F12).

In the BIOS, look for the boot mode setting. Depending on the vendor it can be labelled Boot Mode, UEFI/Legacy, CSM Support, or similar. The setting is usually found under the Boot or Advanced section.

Switch the boot mode to match the partition style on the disk:  

• If the disk uses MBR, set the boot mode to Legacy or enable CSM.   
• If the disk uses GPT, set the boot mode to UEFI and disable CSM.

On some servers, Secure Boot may also need to be disabled temporarily during installation.

Save changes, exit the BIOS, and start the Windows Server installation again.

Option 2: Convert the disk through diskpart

This option fully erases the target disk and converts its partition table. Use it only when there is nothing on the disk that needs to be preserved.

Open the command prompt directly from the Windows Server installer by pressing Shift + F10 on the disk selection screen.

Start diskpart:

diskpart

List the available disks and identify the target by its size:

list disk

The output shows all detected disks with their size and current partition style. Note the number of the disk you want to install Windows on.

Select the target disk (replace N with the actual number from list disk):

select disk N

Wipe the disk and convert its partition table:

clean
convert gpt

For Legacy BIOS, use convert mbr instead of convert gpt.

Exit diskpart and close the console:

exit

Click Refresh on the disk selection screen of the installer. The disk should now be available and the installation will continue.

If the error still appears

If the same error keeps showing after both options have been tried, check the following:

• RAID controller configuration: on dedicated servers, the installer cannot see physical drives until a virtual disk is created on the RAID controller. The controller has its own setup menu, entered during POST with a vendor-specific key (commonly Ctrl + I for Intel, Ctrl + R for LSI/Broadcom, Ctrl + H for older controllers, F10 for HPE).
• Boot device order in BIOS: the correct installation media must be selected as the first boot device.
• Installation media integrity: a corrupted ISO or USB stick can cause similar symptoms. Re-create the installation media if in doubt.

If the issue persists after completing all steps above, contact INTROSERV support and provide:

• the exact error message,
• the server model,
• the RAID controller configuration,
• the Windows Server version being installed.