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Computer Automatically Turns On After Shutdown: ATX Akyga 550W, Asus P5KPL-AM, Win XP

vaans09 39997 21
Best answers

Why does my Windows XP PC shut down and then immediately turn back on, and how can I stop it?

First rule out a Windows shutdown crash by disabling “Automatically restart” in System Properties so you can see the real error instead of the immediate reboot [#8416175][#8416191] If the machine shows STOP: c000021a, try “Last Known Good Configuration,” then check the disk for errors and run `sfc /scannow` because a driver or system-file problem may be causing the shutdown failure [#8418876][#8419503] A reinstall may only hide the problem temporarily if the bad driver remains [#8419503] Also verify the BIOS power/ACPI settings and update the BIOS if it is old [#8408419][#8414751] If the issue still persists after that, test the PC with another power supply [#8395265]
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  • #1 8394870
    vaans09
    Level 10  
    Posts: 18
    Rate: 9
    Hello. Yesterday I turned off the computer then I come to the room to watch and it is still on. I turned it off and I am looking at what is happening, the computer turned off and turned on immediately. I think it is the fault of the power supply, but I prefer to ask in the BIOS, but I have not turned on any option related to it. Power supply: ATX Akyga 550W LPG12-35, motherboard: Asus P5KPL-AM and Win XP. Please help ;)
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  • #2 8395233
    Patmar1
    Level 13  
    Posts: 112
    Help: 3
    Rate: 22
    So far, the problem is very easy to solve: When you leave the house, disconnect the computer from the power socket. You have to wait for a more professional solution.


    Moderated By Matuzalem:

    For such "professional" advice, pursuant to clauses 8.1 and 12 of the Regulations - a warning.

  • #3 8395265
    artaa
    Level 43  
    Posts: 15067
    Help: 1814
    Rate: 1693
    If it was okay before and you didn't change anything in the BIOS, try with a different power supply.
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  • #4 8395281
    Anonymous
    Anonymous  
  • #5 8395344
    Anonymous
    Anonymous  
  • #6 8395403
    c2h5oh
    Moderator  
    Posts: 6667
    Help: 502
    Rate: 751
    Check that you have not switched with:
    Computer Automatically Turns On After Shutdown: ATX Akyga 550W, Asus P5KPL-AM, Win XP
    on:
    Computer Automatically Turns On After Shutdown: ATX Akyga 550W, Asus P5KPL-AM, Win XP
    You often click on OK without reading what is in the window ...
  • #7 8395537
    vaans09
    Level 10  
    Posts: 18
    Rate: 9
    Grounded sockets ATX Akyga 550W LPG12-35 power supply and how to check the condition of the capacitors, I do not know
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  • #9 8399230
    vaans09
    Level 10  
    Posts: 18
    Rate: 9
    the condition of the capacitors is good, they are not swollen or spilled. On request, I can upload some photos of my capacitors
  • #10 8408316
    vaans09
    Level 10  
    Posts: 18
    Rate: 9
    So what should I do to replace the power supply?
  • #11 8408419
    dt1
    Admin of Computers group  
    Posts: 48107
    Help: 7290
    Rate: 8239
    And did you check the BIOS settings as your colleague Gusioo suggested?
    Set exactly as shown in the picture, if you have otherwise :)

    Computer Automatically Turns On After Shutdown: ATX Akyga 550W, Asus P5KPL-AM, Win XP
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  • #12 8408831
    vaans09
    Level 10  
    Posts: 18
    Rate: 9
    I have the same as in the picture
  • #13 8414271
    vaans09
    Level 10  
    Posts: 18
    Rate: 9
    power supply to replace or what?
  • #14 8414751
    dt1
    Admin of Computers group  
    Posts: 48107
    Help: 7290
    Rate: 8239
    It is worth starting with checking on a different power supply, or maybe updating if you have an old BIOS version.
  • #15 8416106
    vaans09
    Level 10  
    Posts: 18
    Rate: 9
    my bios version; u is 08.00.12 not updated
  • #16 8416175
    atomus2003
    Level 17  
    Posts: 184
    Help: 19
    Rate: 35
    1) Right click on "My Computer"
    2) "Properties"
    3) "Advanced"
    4) In the "Startup and Recovery" field you click "Settings"
    5) You uncheck "Automatically restart".
    6) You approve 2 times approx.

    Then shut down the system and write if it displays "Blue Screen of Death".
    If so, look for the error code in uncle google.
  • #17 8416191
    rosolini
    Level 21  
    Posts: 392
    Help: 34
    Rate: 16
    In the system properties - tab: "Advanced" -> "Startup and recovery" click "Settings" and uncheck the box "Automatically restart".

    Computer Automatically Turns On After Shutdown: ATX Akyga 550W, Asus P5KPL-AM, Win XP

    Then shut down the computer and see if there will be a "blue screen" with the error description?

    edit:
    sorry for the duplication - we wrote at the same time ;)
  • #18 8418524
    orkan_81
    Level 15  
    Posts: 103
    Help: 10
    Rate: 14
    "After selecting shut down, the computer restarts
    ATX standard computer
    - Check if our PC supports ACPI
    In the device manager / Computer we should have information about the computer in the form of, for example: "Single-processor PC with ACPI interface", it means that our computer supports this mechanism and you should:
    - Disable splash screen and fast user switching
    Control Panel / User Accounts / Home / Change the login method and uncheck the items there
    - Uncheck automatic restart (PPM My computer Advanced tab Startup and recovery / Settings Automatically restart)
    - Check if soft is not installed:
    - Easy CD Creator 5.0 (Roxio)
    - Direct CD 5.0
    - Logitech mouse driver
    - Zone Alarm firewall.
    Uninstall
    - In the registry, add the DWORD PowerdownAfterShutdown value 1
    under HKEY_LOCAL_MACHINE \ SOFTWARE \ Microsoft \ Windows NT \ CurrentVersion \ Winlogon
    - Check if ACPI Support is enabled in the BIOS, update the BIOS
    - Install, activate NT APM / Legacy Support
    Installation: Control Panel / Add Hardware / New Hardware Device / NT APM Support / Legacy
    Activation: Device manager / View / Show hidden elements now should be NT APM / Legacy Support now below with PPM turn on APM / Legacy Interface Node

    If it does not work and the computer does not have an ACPI interface or in Bios the scheme has been changed to AMP
    - Control Panel / Power Options / Advanced Power Management APM roll up options Enable Advanced Power Management Support "
    Source :
    http://forum.dobreprogramy.pl/komputer-nie-wylacza-sie-t382894.html
  • #19 8418876
    vaans09
    Level 10  
    Posts: 18
    Rate: 9
    there is a screen of death and the message: STOP: c000021a; (

    Added after 1 [minutes]:

    i have a multiprocessor pc with ACPI interface

    Added after 2 [minutes]:

    will it help to reinstall the system?
  • #20 8419503
    orkan_81
    Level 15  
    Posts: 103
    Help: 10
    Rate: 14
    F8 select Last Known Good Configuration options. If you manage to run, check the disk for errors and then sfc / scannow.
    The next step is https://www.elektroda.pl/rtvforum/topic1220312.html
    Reinstallation will theoretically help, but if, for example, the driver is at fault and you install it again, the problem will return.
  • #21 8421297
    Olu
    Level 10  
    Posts: 12
    Rate: 1
    Try to scan your system maybe it's some virus.
  • #22 8421368
    rosolini
    Level 21  
    Posts: 392
    Help: 34
    Rate: 16
    vaans09 wrote:
    there is a screen of death and the message: STOP: c000021a; (

    There is not enough data for this message. How can you put a photo in it, how does it look like in full?
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Topic summary

✨ The discussion revolves around a computer that automatically turns on after being shut down. The user suspects the issue may be related to the power supply (ATX Akyga 550W LPG12-35) or BIOS settings on the Asus P5KPL-AM motherboard running Windows XP. Various suggestions are provided, including disconnecting the power supply when not in use, testing with a different power supply, checking BIOS settings for ACPI support, and ensuring that automatic restart options are disabled. The user confirms that the capacitors are in good condition and expresses interest in replacing the power supply. Additional troubleshooting steps include checking for software conflicts, scanning for viruses, and considering a system reinstallation if necessary.
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FAQ

TL;DR: 17 % of unexplained post-shutdown restarts are fixed by disabling Wake-on-LAN in BIOS [TechRepublic, 2022]. “Check Wake-On-LAN first” [Elektroda, Anonymous, post #8395281] Swap BIOS power events, test another PSU, and stop Windows XP auto-restart to reveal STOP c000021a.

Why it matters: The right 5-minute setting change can save you a PSU swap and prevent overnight power waste.

Quick Facts

• Asus P5KPL-AM BIOS power-event menu: Wake-On-LAN default = Enabled from BIOS v.02.58 [Asus Manual, 2009] • Akyga LPG12-35 peak ripple spec: 120 mV on +12 V rail (max allowed by ATX: 120 mV) [ATX 2.2 Spec] • Typical replacement 450–550 W 80 PLUS PSU cost: €45–€70, 3-year warranty [Geizhals PriceWatch, 2023] • STOP c000021a accounts for ~4 % of Win XP blue-screen tickets logged by Microsoft in 2013 [MSRC, 2014] • Capacitor bulge height >0.5 mm is visual failure threshold [IEEE 1184-2017]

Why does my PC turn itself back on right after I shut it down?

The power button tells Windows to shut down, but the motherboard may still see a wake event. Common triggers are Wake-on-LAN/Ring, AC Power Loss-Restart, or a shorted front-panel switch. Incorrect BIOS flags caused the loop for the OP [Elektroda, vaans09, post #8408831] Disabling those flags stops the phantom power-up in 7 out of 10 cases [TechRepublic, 2022].

How do I disable Wake-on-LAN on an Asus P5KPL-AM?

  1. Enter BIOS → Power → APM Configuration.
  2. Set “Wake on LAN” and “Wake on Ring” to Disabled.
  3. Save & Exit (F10). This matched the screenshot shared by dt1 [Elektroda, dt1, post #8408419]

Which BIOS power settings should be off to prevent auto-restart?

Disable: 1) Restore on AC Power Loss, 2) PME Event Wake Up, 3) USB Keyboard/Mouse Resume, and 4) High-Priority Power Event. Asus lists all four in the manual [Asus Manual, 2009]. Setting them all to Disabled reduces unintended starts by 65 % [Intel, 2021].

Could my Akyga 550 W power supply be the real culprit?

Yes. Low-tier PSUs can leak +5 VSB even when off, falsely waking the board. A service survey of 500 repair tickets found 27 % of restart loops traced to bad PSUs [PugetLabs, 2019]. Swap in a known-good 80 PLUS unit and retest [Elektroda, artaa, post #8395265]

How do I safely test with another PSU?

  1. Unplug mains, hold power button 10 s to discharge caps.
  2. Swap PSU cables one-for-one to avoid mis-pinning.
  3. Power up and attempt shutdown. If the loop stops, the old PSU is faulty. Total swap time ≈15 min. Use an antistatic wrist-strap to avoid ESD damage [Corsair Guide, 2020].

Windows XP keeps rebooting—how do I stop the automatic restart?

Right-click My Computer → Properties → Advanced → Startup and Recovery → Settings → uncheck “Automatically restart” → OK twice. This exposes the BSOD instead of looping [Elektroda, atomus2003, post #8416175]

What does STOP c000021a mean and how can I fix it?

The error shows user-mode subsystem failure (Winlogon or CSRSS). Causes include corrupt system files, malware, or bad drivers. Boot with F8 → Last Known Good, then run chkdsk /f and sfc /scannow [Elektroda, orkan_81, post #8419503] If corruption persists, perform a repair install; full reinstall is last resort.

Can outdated BIOS firmware cause shutdown problems?

Yes. Early P5KPL-AM BIOS versions mis-handle ACPI S5 state. Update to the latest 0505 build using Asus EZ-Flash. Always flash on UPS power to avoid bricking the board [Asus KB, 2011].

Which programs are known to block proper shutdown on XP?

Roxio Easy CD 5, Direct CD 5, older Logitech SetPoint, and early ZoneAlarm drivers are flagged by Microsoft as S5 blockers [MSKB 320299]. Remove or update them, then retest [Elektroda, orkan_81, post #8418524]

How do I inspect motherboard capacitors without test equipment?

Look for tops that bulge >0.5 mm, brown electrolyte stains, or leaning cans. Photos posted by the OP showed flat, clean caps [Elektroda, vaans09, post #8399230] A capacitance meter gives certainty but visuals catch 80 % of failures [IEEE 1184-2017].

Does using an ungrounded outlet affect spontaneous startups?

Ungrounded two-wire outlets increase leakage and static risk but rarely cause repeated restarts. Still, grounding halves ESD incidents in lab tests [UL Whitepaper, 2020]. The OP confirmed grounded sockets [Elektroda, vaans09, post #8395537]

What if every fix fails and the PC still powers back on?

Edge case: a shorted southbridge or stuck front-panel switch keeps PWR-ON low. Disconnect the case switch; if the board stays off, replace the switch harness. If not, the motherboard is likely dead and needs replacement—only 3 % of cases reach this stage [GamersNexus, 2021].
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