On recent HP computers, UEFI firmware has largely replaced the traditional BIOS. Switching from UEFI mode to Legacy mode (also known as CSM) remains a sought-after manipulation, particularly for installing an older operating system or booting from a non-UEFI compatible medium. The procedure varies depending on the generation of HP hardware, and some machines now block this option.
Secure Boot and Legacy Lock on Recent HP PCs
Before looking for the Legacy option in the BIOS, a technical point deserves attention. HP increasingly blocks Legacy Support on its recent professional laptops, particularly the EliteBook, ProBook, and ZBook ranges delivered with Windows 11. The Legacy/CSM menu is either completely absent from the firmware or grayed out when Secure Boot is enabled.
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This lockout is not a bug. HP has published a notice (Customer Advisory, updated late 2023) confirming the gradual deprecation of Legacy BIOS support on certain professional PCs. On these machines, the only option is to operate in native UEFI mode.
For consumer ranges (Pavilion, HP Laptop) or older professional models, the option generally remains accessible. Therefore, before any manipulation, it is essential to check if your HP model still allows switching. A detailed guide explaining how to change UEFI mode to legacy on HP quickly situates the scenarios based on your machine’s generation.
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Accessing the HP BIOS and Locating the Legacy Boot Option
The key to access the BIOS varies by HP model. On most laptops and desktops, it is the F10 key that should be pressed immediately after powering on, before the HP logo disappears. On some models, the Escape key first opens a boot menu, from which “BIOS Setup” is selected.
Navigating the HP Firmware Menus
Once in the BIOS, the menu structure depends on the firmware version. On HP machines that retain the option, here is the usual path:
- “System Configuration” or “Advanced” tab, then “Boot Options” submenu
- Look for the line “Legacy Support” or “CSM Support” and set it to “Enabled”
- Disable Secure Boot (mandatory, as Legacy and Secure Boot are mutually exclusive)
- Change the boot order to place the desired device (hard drive, USB drive) in the first position
After these changes, save with F10 and confirm. The system will then restart in Legacy mode.
Verification Code on Restart
On many HP laptops, disabling Secure Boot triggers a confirmation screen on the next restart. HP requires entering a numeric code displayed on the screen to validate the change. This security step prevents accidental or malicious modification of the boot mode. Without this validation, the firmware automatically reverts to the previous settings.
Technical Consequences of Switching to Legacy Mode on HP
Changing the boot mode is not limited to checking a box. Switching from UEFI to Legacy has direct implications on the machine’s operation.
Partition Table: GPT vs MBR
The UEFI mode uses the GPT partition scheme. The Legacy mode relies on MBR. If your system disk is formatted as GPT (which is the case for almost all machines delivered with Windows 10 or 11), the system will not boot after switching to Legacy without prior conversion of the disk.
Two options then arise:
- Convert the disk from GPT to MBR using a dedicated tool (like mbr2gpt in reverse, or third-party partition management software), knowing that this operation carries a risk of data loss if not executed properly
- Reinstall the operating system from scratch on a disk reformatted to MBR, which remains the most reliable method
- Fully back up your data before any manipulation, regardless of the chosen method
In both cases, a complete backup to an external medium is the minimum precaution.
Loss of Features on Recent Machines
On HP Pavilion and HP Laptop ranges equipped with recent AMD Ryzen processors (7000U/8000U series), enabling Legacy mode automatically disables “Modern Standby.” User feedback on HP Support forums reports increased power consumption in sleep mode and wake-up issues after this change. HP BIOS release notes (references F.20/F.22 for Pavilion 15 series) confirm this behavior.
Windows 11 and Legacy Mode: A Documented Dead End
Since the introduction of Windows 11, Microsoft no longer officially tests installation scenarios on Legacy firmware. The Media Creation Tool generates USB drives intended for UEFI firmware. Installing Windows 11 in Legacy mode is not a scenario supported by Microsoft.
If your goal is to run Windows 11, switching to Legacy has no technical benefit. However, to install an older system (Windows 7, certain Linux distributions that do not handle UEFI well, or a low-level diagnostic tool), Legacy mode remains sometimes the only viable solution.
The question to ask before modifying the firmware is therefore simple: which operating system or tool needs to boot on this machine? If the answer is UEFI compatible, switching to Legacy creates more problems than it solves.
Legacy mode remains accessible on part of the HP fleet, but the trend is clear. Recent professional machines are progressively locking this option, and modern operating systems no longer officially support it. Before modifying the firmware of an HP computer, checking model compatibility and backing up data remain the two steps that condition everything else.