#Requires -Version 5.1
<#
    JbTecWiz Support Centre -- generated fix script

    Fault : Microsoft Defender will not turn on
    Fix   : Remove the previous product's registration completely
    Source: https://jbtecwiz.com/support/win-sec-defender-off

    Run as     : Elevated PowerShell
    Expect     : 30 minutes
    Risk       : medium
    Reversible : yes

    WHEN THIS IS THE RIGHT FIX
    Another antivirus has been installed and removed.

    HOW TO UNDO IT
    Reinstalling the third-party product restores its registration.

    This script walks the fix one step at a time and asks before each
    one. Steps with no command are things you do yourself -- it prints
    those and waits. Run with -DryRun to print without executing.

    --------------------------------------------------------------------
    NO WARRANTY - USE AT YOUR OWN RISK

    This script is provided by JbTecWiz as-is and with no warranty of any
    kind, express or implied. You run it entirely at your own risk.

    JbTecWiz accepts no liability for any loss or damage arising from its
    use, including but not limited to data loss, downtime, or configuration
    changes that turn out to be wrong for your system.

    You are responsible for reading this script before running it, for
    satisfying yourself that it suits the machine in front of you, and for
    having a working backup first. Some steps cannot be undone.
    --------------------------------------------------------------------
#>

[CmdletBinding()]
param(
    # Print every step and command without running anything.
    [switch]$DryRun,
    # Do not ask before each step. Read the script first if you use this.
    [switch]$Unattended
)

$ErrorActionPreference = 'Stop'
$script:Failed = 0

function Write-Rule { param([string]$Text)
    Write-Host ''
    Write-Host ('-' * 70) -ForegroundColor DarkGray
    if ($Text) { Write-Host $Text -ForegroundColor Cyan }
}

function Show-Prose { param([string]$Text, [string]$Colour = "Gray")
    if (-not $Text) { return }
    $words = $Text -split "\s+"; $line = "  "
    foreach ($w in $words) {
        if (($line.Length + $w.Length) -gt 74) { Write-Host $line -ForegroundColor $Colour; $line = "  " }
        $line += "$w "
    }
    if ($line.Trim()) { Write-Host $line -ForegroundColor $Colour }
}

function Invoke-Step {
    param(
        [int]$Number, [string]$Do, [string]$Why,
        [scriptblock]$Command, [switch]$Manual, [string]$Shell = "powershell"
    )
    Write-Rule "  Step $Number of 5"
    Show-Prose $Do "White"
    if ($Why) { Write-Host ""; Show-Prose $Why "DarkGray" }

    if ($Manual) {
        Write-Host ''
        Write-Host '  -> Do this yourself, then press Enter to carry on.' -ForegroundColor Yellow
        if (-not $Unattended -and -not $DryRun) { [void](Read-Host) }
        return
    }

    Write-Host ''
    foreach ($l in ($Command.ToString().Trim() -split "`n")) {
        Write-Host ("    " + $l.Trim()) -ForegroundColor Green
    }
    Write-Host ''

    if ($DryRun) { Write-Host "  (dry run -- not executed)" -ForegroundColor DarkGray; return }
    if (-not $Unattended) {
        $a = Read-Host "  Run this step? [Y]es / [S]kip / [Q]uit"
        if ($a -match "^[Qq]") { Write-Host "  Stopped at your request."; exit 0 }
        if ($a -match "^[Ss]") { Write-Host "  Skipped." -ForegroundColor DarkGray; return }
    }
    try { & $Command }
    catch {
        $script:Failed++
        Write-Host ("  Step $Number failed: " + $_.Exception.Message) -ForegroundColor Red
        Show-Prose "The rest of the fix may depend on this. Read the write-up before carrying on." "Red"
        if (-not $Unattended) {
            $c = Read-Host "  Carry on anyway? [y/N]"
            if ($c -notmatch "^[Yy]") { exit 1 }
        }
    }
}

Write-Rule
Write-Host '  Microsoft Defender will not turn on' -ForegroundColor White
Write-Host '  Remove the previous product''s registration completely' -ForegroundColor Cyan
Write-Host ''
Write-Host '  Risk: medium   Reversible   30 minutes'
Write-Host ''
Show-Prose 'No warranty. Use at your own risk - JbTecWiz accepts no liability. Read it before you run it, and have a backup.' 'DarkYellow'
Write-Rule

if (-not $Unattended -and -not $DryRun) {
    $go = Read-Host '  Ready? [y/N]'
    if ($go -notmatch "^[Yy]") { Write-Host "  Nothing was changed."; exit 0 }
}

Invoke-Step -Number 1 -Do 'See what the Security Centre still believes is installed.' -Why 'Defender stands down while another product is registered here. If the old product is listed but no longer installed, Defender will stay off no matter what is clicked in Settings.' -Command {
    Get-CimInstance -Namespace root\SecurityCenter2 -ClassName AntiVirusProduct | Format-List displayName,productState,pathToSignedProductExe
}

Invoke-Step -Number 2 -Do 'Run the vendor''s own removal tool. Every major antivirus publishes one, and it removes the filter drivers and registrations a normal uninstall leaves behind.' -Manual

Invoke-Step -Number 3 -Do 'Restart, then check the registration list again -- the stale entry should be gone.' -Manual

Invoke-Step -Number 4 -Do 'Start Defender''s services.' -Command {
    Set-Service WinDefend -StartupType Automatic -ErrorAction SilentlyContinue
    Start-Service WinDefend
    Start-Service SecurityHealthService
}

Invoke-Step -Number 5 -Do 'Update the definitions, which will be months old.' -Command {
    Update-MpSignature
}

Write-Rule "  Confirm it worked"
Show-Prose 'Real-time protection is on and the definitions are current.' 'White'
Write-Host ''
if (-not $DryRun) {
    Get-MpComputerStatus | Format-List AMServiceEnabled,RealTimeProtectionEnabled,AntivirusSignatureLastUpdated,AMRunningMode
}

Write-Rule
if ($script:Failed -gt 0) {
    Write-Host ("  Finished with " + $script:Failed + " failed step(s).") -ForegroundColor Yellow
    Show-Prose 'Read the full write-up at https://jbtecwiz.com/support/win-sec-defender-off' 'Yellow'
} else {
    Write-Host '  Finished.' -ForegroundColor Green
}
Write-Host ''
Show-Prose 'To undo: Reinstalling the third-party product restores its registration.' 'DarkGray'
Write-Rule