Stuck on "mup.sys" during boot up

Discussion in 'Windows XP Help' started by Matt B, Jul 9, 2003.

  1. Matt B

    Matt B Guest

    We are having this problem on several systems at my office, as well as a few
    of our home users. One in every ten or so times we boot up a Windows XP
    system, it will hang on start-up. When I restart and boot-up in safe mode,
    each system appears to hang on a file called "mup.sys".

    There are a LOT of other people having this problem (simply do a Google
    search). I've heard that this problem has to do with PCI cards, USB 2.0
    cards, USB mice, Network cards, a corrupt installation, and possibly the
    FBI's Carnivore problem checking my system. Personally, I've tried about
    every "fix" that I have found, yet each system will still hang on start-up
    ever so often.

    Does anyone (including you Microsoft people) know what is going on here? Is
    there a service running that I can turn off so that this won't happen?
    Thanks for any help...
    Matt B, Jul 9, 2003
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  2. Matt B

    FastLane Guest

    FastLane, Jul 9, 2003
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  3. Matt B

    jym Guest

    jym, Jul 9, 2003
  4. Matt B


    Jun 29, 2006
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    mup.sys and 'safe mode'

    There are no less than 3 reasons for this error. Hardware 40%, software 40% and unknown 20%. If you can boot normally but cannot boot into 'safe mode' I think I have the definitive answer.

    This error is hardware independent and only occurs on systems NOT running a genuine copy of XP. You may need to borrow such a copy to test both the problem and the solution. Please be sure to re-install your genuine XP disk once you have completed testing. However the advice given under "CONCLUSIONS" below might well apply to ALL XP installations.

    1) How to set up an XP system with no "safe mode" error.
    2) How to bring about the error.
    3) How to remove it.
    4) How to prove the cause, and benefit from the knowledge.

    1) Take any machine capable of running XP-Pro and fit a clean HDD.
    2) Set up XP+SP2. Stay offline for now.
    3) Optionally install a software firewall and turn its logs on. From these you can indepentently verify the conclusions below.
    4) Reboot and test "safe mode". It will work.
    5) Reboot, set a restore point (see 9 and 11 below), then go online and request a download of all MS Security Updates (from control panel / security center). It sent me 24,
    6) Shutdown. Your machine will install the updates before switching itself off.
    7) Restart the computer in 'safe mode' and it will freeze at MUP.SYS
    8) Restart Windows normally, staying off-line.
    9) From (control panel / add or remove programs) remove all security updates. Restore from the "Restore point"
    10) Reboot the machine. 'Safe mode" now works correctly.
    11) On the 3 unrelated machines I tested the 'Restore point' was not needed, but you can't be too safe.

    1) Security Upgrades are not only for your personal security. They also benefit Microsoft and agencies friendly with Microsoft.
    2) The Security Upgrades are downloaded via SVCHOST.EXE. Data is also uploaded (in most cases without your knowledge) to many sites by SVCHOST.EXE.
    3) Although SVCHOST.EXE is an essential file, many software firewalls can limit it to the "Trusted Zone"- ie and 169.255.x.x (Kerio will do it, as will others)
    4) Limiting net access to SVCHOST.EXE has NO appreciable effects except for preventing-
    a) downloads of MS Security Updates
    b) auto setting of the machine's RTC
    c) the mysterious sending of data to tens of unknown IPs 100+ times a day.

    5) These effects can be easily overcome as follows-
    a) Run a full suite of freeware programs. SpybotS&D, Spyware Doctor, SpywareBlaster, AVGFree, Kerio, Peer Guardian, RegscrubXP and Adaware are among the better ones. Combined they aurguably provide MORE security than MS Security Upgrades.
    b) Most freeware clocks will download only from sites you specify and without any need of SVCHOST.EXE.
    c) I don't like my machine talking to strangers. I'm happy to lose this "undocumented feature".

    HOW TO FIX a system that is already 'infected' with the "Safe Mode" bug-
    1) Get a software firewall which can limit SVCHOST.EXE to your 'trusted zone'.
    2) Install all of the above recommended software or equivalent, update and run it regularly.
    3) Uninstall ALL MS "Security Upgrades" and re-boot. You will once again have 'Safe Mode' operating normally.
    4) Stop using all MS software which requires access to the internet. Absolutely block IE, Outlook etc with your software firewall. Download alternative software- "Open Source" where possible.
    5) Keep an eye open for new software wanting access to the 'outside world'. I have very few programs that MUST be open to untrusted zones- my Browser, Email, the freeware security programs, and a file sharer. Even Kerio is limited to the trusted zone.
    paws0z, Jun 29, 2006
  5. Matt B


    May 30, 2007
    Likes Received:

    I have experienced the same problem on several PCs. Sometimes I was able to start in safe mode, but in worst cases computer acted almost dead. In this cases I didn't even get windows startup menu (to choose safe mode or similar).
    But everytime the same steps solved the problem:
    - boot computer from Windows CD and choose repair (R)
    - from command prompt run: chkdsk /r
    - when checkdisk finishes, remove Windows CD and boot WindowsXP normally.

    Before that I tried zillion tips I found on web, but none of them helped.

    Nika Lampe
    nika, May 30, 2007
  6. Matt B


    Jul 28, 2007
    Likes Received:
    Coimbra, Portugal
    Restart the computer (Windows XP Pro) in 'safe mode' and it will freeze at "MUP.SYS"

    That same problem was happening to me on a XP SP2 Intel Pentium MMX machine and I had to re-install XP and SP2 about 3 times before I figured where the problem was..

    When I instaled SP2, I also installed a windows update (reliability update) for intel processors (which you can find here:
    and the reboot problem started...
    In my last instalation, I didn't do that update which microsoft tells it is advisable to do... and all my system is stable again and no more cycling reboots.
    I did ALL other critical updates and non critical updates and only didn't this one and the system has been stable for a few weeks now...

    If you want my opinion, disable auto-instalation on microsoft updates (even the critical ones) and set it to tell you when something new is there... and you won't have misterious problems like this again.

    When I had the reboots, If I did a safe reboot-restart, my system was freezing at MUP.SYS and it wouldn't move anywhere...

    I've seen on other foruns that the problem was on the SP2 package which isn't really true....all my system is stable now.
    Tried also that chkdsk and other things and all them FAILED big time!

    Pedro Matos Rito
    plmrito, Jul 28, 2007
  7. Matt B


    Aug 3, 2007
    Likes Received:
    MUP.SYS = solved XP_SP2 wih new user_ID account

    Folks, this was not an easy solution. Could not log into my PC with F8 as the "Administrator".
    Stuck on "mup.sys".
    Fixed-it and now it works ok. Here is how.
    Created a new-user account from the Control Pannel (Add User) and deleted my old-user account from the Control Pannel (Remove User, etc)
    Careful: lost all emails from the old account & had to reinstall the Thunderbird incoming and outgoing server names.
    Cleaned-up the HDD with Norton System Works, fixed registries with same and with Registry Mechanic.
    Defragmented the HDD last.
    Noticed faster boot-up time.
    Regards, etc.
    xeu, Aug 3, 2007
  8. Matt B


    May 14, 2008
    Likes Received:
    Will this still happen in the new XP Pro SP3 ?

    So these problems are all caused by viruses ? There' s another nasty thing.

    When u try system restore- it comes up "cannot lock volume, its being used by another process".

    will this still happen in XP pro SP3 ?
    auto78900, May 14, 2008
  9. Matt B


    May 6, 2009
    Likes Received:

    I've sorted this out on probably a dozen genuine installs of Windows.
    Yeti, May 6, 2009
  10. Matt B


    Oct 20, 2009
    Likes Received:
    Found a fix!

    I had the same problem hanging on mup.sys. I loaded to a black screen with a large white arrow in normal mode. This article saved my computer and left all of my files intact. It's basically doing a system restore through DOS.;en-us;Q307545\
    It's long and involved, but I tried absolutely EVERYTHING else and I thought this was going to be the first time I couldn't fix my computer.
    sylvie1313, Oct 20, 2009
  11. Matt B


    Sep 21, 2010
    Likes Received:
    I could solve this problem

    I could solve Mup.sys reboot problem in this way.

    1. Boot pc with windows xp cd in repair mode or use any live cd like BARTPE builder cd
    2. It goes to command mode.
    3. Run chkdsk on c: drive
    4. It automatically fixes any errors
    5. done.

    pvdesnips, Sep 21, 2010
  12. Matt B


    Mar 6, 2012
    Likes Received:
    i had the same problem hanging on welcome screen of windows xp.during installation setup.i also use safe boot,but it also hangs on mup.sys.By a help of a friend troubleshooting using 2 pc.working and not working.we've tried lots of things what internet says but none of them solved our problem.Then we manage to use 2 hdd on a working pc,and use chkdsk /p /r on repair setup using windows xp installer.We fixed the bad sectors on the hdd, and try it again on its original cpu.But still it doesn't sovlve the problem yet.connecting 2 hdd again in working pc,we got the silly idea of copying the working \windows\system32\drivers folder to the other one that is not working and try to see if we will hit the stone.And the funny thing is IT WORKS.hehe.the windows xp installation resume after the welcome screen that hangs before.we're using windows XP Pro SP3.
    Last edited: Mar 6, 2012
    chrizhen, Mar 6, 2012
  13. Matt B


    May 16, 2013
    Likes Received:
    I SOLVED MY PROBLEM. See this message:
    I HAD USB mouse, which causes the error, especially when it was plugged.
    (I have detected that after testing the BIOS option for USB enable/disable).

    Here i have seen other solutions too -


    2) (in the middle of the topic, someone said TO roll back to old USB instalation state, and that solved problem !!!!!)
    tazosmr, Jan 21, 2014
  14. Matt B


    May 16, 2013
    Likes Received:
    I know, this is old TOPIC, but this problem is actual, so i posted a solution.
    My fix was the following:
    So, i unplagged it, and then with LAPTOP's built in mouse, i browsed INTERNET and i founded solutions at the above links.

    My FIX was following:
    after i uninstalled the MOUSE Driver from DEVICE MANAGER, then i copied usbport.sys,usbui.dll, usbhub.sys, usbuhci.sys files from


    and after that, i pluged my mouse, and windows works normally!!
    tazosmr, Jan 22, 2014
  15. Matt B


    May 16, 2013
    Likes Received:
    Here are other solutions too -
    tazosmr, Feb 14, 2014
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