How do I fix a computer that says “operating system not found” when booting?

kenneth May 22, 2015
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UPDATE (October 2017): Please find an updated article on how to fix the “operating not found” error here Operating System Not Found? Here's How to Fix It Operating System Not Found? Here's How to Fix It "Operating system not found" must be the most shocking error message out there. Relax! Your data is still there. Let us show you how to get it all back. Read More .

Kenneth asks:

When I boot my Acer TravelMate P643M with Phoenix bios I get the message “operating system not found”. Pressing CTRL+ALT+DEL reboots the computer. I can’t change the boot priority. I have tried removing my CMOS battery but it doesn’t change anything.

Bruce’s reply:

Depending on the BIOS used by the system, the error message that appears could also be “Missing operating system”. There are both hardware and software issues that may be causing either of these error messages to appear which we will look at in turn.

Is your hard drive detected by the BIOS?

There is the possibility that the connection to the drive has been jarred loose. The documentation for your device available from the Acer website is next to useless and I cannot find a decent shot of the underside of the computer but there should be a means to access the hard drive of your computer via a covered opening without resorting to major disassembly. On most laptops it only requires a small Philips screwdriver to remove it. Just open up the cover and ensure the drive is firmly seated in the connector.

If the drive is securely connected, you may have a failed hard drive. In this case, the drive needs to be replaced, your OS reinstalled (if you have the correct media), and your data restored from backups. You have been making backups, right?

The software side

If you can see your hard drive in the BIOS, there is a problem with the boot record or the BCD (Boot Configuration Database). To fix this, you need to have a bootable repair disc created from your system earlier or a Windows installation disc for the version of Windows currently installed on the machine. The recovery discs provided by OEMs or created by their recovery disc creation software will not work for this. They only place a new copy of the factory installed image on the system and are not the same as the Windows installation DVD.

If you have the installation disc, boot from it.

Install Disc 1

After selecting your preferences, click Next.

Install Disc 2

Click ‘Repair your computer’.

If you are using a Windows repair disc instead of the installation disc, when you boot you will get the following dialog.

Repair Disc 1

Because this disc was created on the same machine (or it should have been), then language will be pre-selected and you will not be able to change it, so select the appropriate keyboard type and click Next.

From here, the steps are the same no matter which disc you are using. In both cases, the system will search for all Windows installations it can find and give you a list of Windows installations it found on the system.

Repair Disc 2

Select your operating system from the list. The Load Drivers option should not be required for most user systems unless you are using RAID in which case you may not see any operating systems in the list.

After you select the OS, you will see the recovery options dialog box.

Repair Disc 3

For this problem, we have two options here that we can use to solve the problem. Startup Repair is an automatic process that will run a series of checks and try to fix anything that is preventing Windows from starting. When it is done, it will present a log of the checks it performed, the results of those tests, and any actions taken to fix the problem.

The other option is to use the command prompt to manually type in a few quick commands to resolve the issue. This method tends to be faster since it does not do all of the work of the Startup Repair option which, in this instance, should not be required.

Repair Disc 4

At the command prompt, issue the following commands, pressing Enter after each one:

bootrec /fixmbr
bootrec /fixboot
bootrec /rebuildbcd

The first command will write a new master boot record without touching the partition tables which reside at the end of the sector.  The second command will write a new boot sector on the system partition.  The third command will search the drive for OS installations that are not reflected in the current boot menu and offer the user the opportunity to add them to the menu.

The message displayed after that third command may be a little bit misleading.  It does make it seem like it didn’t find a Windows installation on the machine where I ran the command which is not the case.  It appears that it is the count of Windows installations that are not currently reflected in the BCD.

Finally, the ‘exit’ command closes the command prompt.

You are now ready to click on the Restart button on the system recovery dialog box to reboot your computer and verify that the fix is successful.

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  1. Tshediso
    November 7, 2018 at 10:22 am

    My Toshiba laptop auto updated and the wfi ran out so now it have been stucked and on the screen it writes "resoring previous version of windows.
    This is the 3rd month doing that thing so i think windows crashed

    I would be more than grateful for any help i can get.

  2. kamil abdulaziz
    October 24, 2017 at 2:46 pm

    one day when i open my lg laptop it doesn't work. it says missing operating system. and then i try to reinstall other windows (operating system) it also says missing operating system. if any one can help me please.

  3. Chinmay Joshi
    August 24, 2017 at 9:27 pm

    Yes it worked for mee I have windows 10 and when I started my laptopit started beeping and then a message is displayed that no operating system found on your device but this solution worked for me because I'm having my windows installation disk and without that I might not be able to do this .... Thanks for this solution ?

  4. fieryeyes
    February 4, 2017 at 1:00 pm

    my sony vios keep saying operating system not found when i opened it..can i replace my hard drive with a new one? and how much it cost?

  5. Magnus
    January 29, 2017 at 5:09 am

    I get the same message when i start the old laptop. It had win Vista installed on it, but I have no win Vista DVD and the hard drive has been formated. So i wonder how on earth I will be able to get a new OS into the old laptop. Been looking at these smaller OS systems like Linux mint, phoenix OS etc etc. It doesn't matter if i have to use a USB boot thing to make it run. Just wanna get it running again

  6. Delena Duffy
    January 10, 2017 at 2:41 am

    Your answer is awesome and very helpful thank you for adding the codes. Your time and effort is greatly appreciated.

  7. Samson joseph
    September 19, 2016 at 5:05 pm

    I cannot go forward after switch on the laptop .it appears 'operating system not found' what is the remedy?```i have somany important files in it.....

    • Mugs
      September 27, 2016 at 1:10 pm

      it means either your hard drive has crashed

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