What if I delete EFI partition from my drive?

Without that partition your computer will almost certainly not boot. The UEFI firmware on your PC looks for a partition containing the system bootloader to execute and having deleted that partition it will simply be waiting for you to insert some kind of bootable CD-ROM or DVD that can install a bootloader and potentially an operating system.

It will not simply "fall back" to a "legacy" (BIOS based) boot, because it is not that simple.

UEFI expects a GPT partition format on the disk, the Windows BIOS bootloader expects an MBR partition scheme.
as you (probably) do not have an MBR partitioned disk then you will likely not have set up a boot sector on the disk pointing to a valid bootloader that the BIOS will be able to execute.
you need to set "legacy" boot mode in the BIOS.

Windows will also refuse to install to an MBR partitioned disk while the system firmware is set to UEFI mode, it will also refuse to install to a GPT disk on a system with a legacy BIOS setup. Microsoft has simply decided not to support these cases in their bootloaders.

Windows support for disk partitions can be found at Windows support for hard disks that are larger than 2 TB

System        BIOS + MBR   UEFI + GPT                  BIOS + GPT                   UEFI + MBR
Windows 7     Supported    Supported; (64-bit only)   Boot volume not supported     Boot volume not supported
Windows Vist  Supported    Supported; (64-bit only)   Boot volume not supported     Boot volume not supported
Windows XP    Supported    Not supported              Boot volume not supported     Boot volume not supported

What if I delete EFI partition from my drive?

Related

Recent Posts