Make a Windows PC never sleep, hibernate or get shut down from the Start menu: powercfg GUIDs + Explorer policies

Keep an unattended Windows 10/11 machine (laptop or desktop) running 24/7 for a background service. Users should not be able to sleep it or shut it down from the UI by accident, and Windows Update should not reboot it while someone is logged on.

$bk='C:\ProgramData\alive-backup'; New-Item -ItemType Directory -Force $bk | Out-Null
$act=(powercfg /getactivescheme) -replace '.*:\s*([0-9a-f-]{36}).*','$1'
powercfg /export "$bk\active-scheme.pow" $act
reg export "HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies" "$bk\hklm-policies.reg" /y
$B='4f971e89-eebd-4455-a8de-9e59040e7347'; $SL='238c9fa8-0aad-41ed-83f4-97be242c8f20'
$set=@(@($B,'5ca83367-6e45-459f-a27b-476b1d01c936',0),  # lid close: do nothing
       @($B,'7648efa3-dd9c-4e3e-b566-50f929386280',0),  # power button: do nothing
       @($B,'96996bc0-ad50-47ec-923b-6f41874dd9eb',0),  # sleep button: do nothing
       @($SL,'29f6c1db-86da-48c5-9fdb-f2b67b1f44da',0), # sleep after: never
       @($SL,'9d7815a6-7ee4-497e-8888-515a05f02364',0), # hibernate after: never
       @($SL,'94ac6d29-73ce-41a6-809f-6363ba21b47e',0), # hybrid sleep: off
       @($SL,'7bc4a2f9-d8fc-4469-b07b-33eb785aaca0',0)) # unattended sleep timeout: never
$schemes = powercfg /list | Select-String '([0-9a-f]{8}-[0-9a-f-]{27})' | % { $_.Matches[0].Value }
foreach($s in $schemes){ foreach($x in $set){ powercfg /setacvalueindex $s $x[0] $x[1] $x[2]; powercfg /setdcvalueindex $s $x[0] $x[1] $x[2] } }
powercfg /setactive $act; powercfg /h off
$e='HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\Explorer'; New-Item -Force $e -ea 0|Out-Null
Set-ItemProperty $e NoClose 1 -Type DWord; Set-ItemProperty $e HidePowerOptions 1 -Type DWord
Set-ItemProperty 'HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System' shutdownwithoutlogon 0 -Type DWord
$wu='HKLM:\SOFTWARE\Policies\Microsoft\Windows\WindowsUpdate\AU'; New-Item -Force $wu -ea 0|Out-Null
Set-ItemProperty $wu NoAutoRebootWithLoggedOnUsers 1 -Type DWord

Apply to all schemes, both AC and DC, so that switching plans or unplugging does not undo it. To push the script through a remote exec channel without quoting problems: B=$(iconv -f UTF-8 -t UTF-16LE s.ps1 | base64) then powershell -NoProfile -EncodedCommand $B.

powercfg /q <scheme> <sub> <setting> read back 0x00000000 for AC and DC on every setting, HibernateEnabled was 0, and NoClose/HidePowerOptions were 1.

Holding the power button for 4 s still forces power-off. After any reboot, per-user autostart waits for a login unless autologon is configured.