MBR2GPT cannot create EFI system partition

Question

Hello all, hope everyone is well. Sorry for yet another w10<w11 post but I’ve really tried my hardest to use search functions and other YouTube to figure this out and I’m still stumped.

I’m trying to upgrade to W11 but can’t do so because if I enable UEFI then my BIOS no longer boots or even sees my windows installation anymore. It seems the way to fix this is to reformat my drive to GPT styled partitions? I’ve tried using the built in MBR2GPT on windows and just running into problem after problem. I thought it finally had it figured out but now it leaves me with

“Cannot create EFI system partition. Error: 0x000036B7”

On my SSD I have 2 partitions, first is one labeled "New Volume" and is 497MB, Second is my main partition labeled "windows C" and has 931GB of space of which 120GB is free.

I read somewhere else that this tool only works with 2 partitions on a drive set in a very specific way but I feel very reluctant to just “delete” random partitions on my drive or start splitting them.

What would the next steps be from here? I'm frustrated because I want the free windows 11 upgrade since I paid for windows 10 and should be eligible, my hardware all meets requirements but this software format error wont allow me to do it.

thank you all for any help

Answer 1

Hi Jarod B,

Can you run this script in PowerShell admin, it doesn't change any settings but might point to where you need to adjust your system to convert to EFI without re-installing.

# Requires admin rights
If (-NOT ([Security.Principal.WindowsPrincipal] [Security.Principal.WindowsIdentity]::GetCurrent()).IsInRole([Security.Principal.WindowsBuiltInRole] "Administrator")) {
    Write-Warning "Please run this script as Administrator."
    Exit
}

# Setup
$timestamp = Get-Date -Format "yyyy-MM-dd_HH-mm-ss"
$logPath = "$env:TEMP\MBR2GPT_Check_$timestamp.log"
$diskpartScript = "$env:TEMP\disklayout.txt"

# Helper: Log and display
function Log {
    param([string]$message)
    Write-Host $message
    Add-Content -Path $logPath -Value $message
}

# Step 1: Create DiskPart script
@"
select disk 0
list partition
exit
"@ | Set-Content $diskpartScript

# Step 2: Show disk layout
Log "`n=== Disk Layout ==="
$diskpartOutput = diskpart /s $diskpartScript 2>&1
$diskpartOutput | ForEach-Object { Log $_ }

# Step 3: Check BitLocker status
Log "`n=== BitLocker Status (C:) ==="
$bitlockerOutput = manage-bde -status C: 2>&1
$bitlockerOutput | ForEach-Object { Log $_ }

# Step 4: Run MBR2GPT validation
Log "`n=== MBR2GPT Validation ==="
$validation = Start-Process -FilePath "mbr2gpt.exe" -ArgumentList "/validate /disk:0 /allowFullOS" -Wait -PassThru -NoNewWindow -RedirectStandardOutput "$env:TEMP\mbr2gpt_out.txt" -RedirectStandardError "$env:TEMP\mbr2gpt_err.txt"

# Log MBR2GPT output
Get-Content "$env:TEMP\mbr2gpt_out.txt","$env:TEMP\mbr2gpt_err.txt" | ForEach-Object { Log $_ }

# Step 5: Decision logic
if ($validation.ExitCode -eq 0) {
    Log "`n✅ Validation passed. You can now run:"
    Log "  mbr2gpt /convert /disk:0 /allowFullOS"
    Log "Then reboot and switch BIOS to UEFI mode."
} else {
    Log "`n❌ Validation failed. Review the output above for details."
    Log "Common issues include:"
    Log "- Disk is already GPT or not MBR"
    Log "- Not enough unallocated space for EFI partition"
    Log "- BitLocker not suspended"
    Log "- OS partition not set as active"
}

# Final note
Log "`n📝 Full log saved to: $logPath"

Answer 2

This error is not due to your number of partitions. Please provide an image of disk management.