Fix Missing Operating System: Windows 7 or 8 (2015 Update)

Oliver SK.

8 years ago

After starting my PC today, I was staring at a little message on my screen that said “Missing operating system”. At first I was a little bit shocked, but of course I knew that this *most often* only means that either my disk has some small disk errors or my master boot record is damaged.

Unfortunately, the solution is not 42, so let’s find out what we can do about it! If you’re stuck in X:/sources after booting with your DVD that’s good news!

Run chkdsk to repair disk errors

First of all, don’t panic! If you panic and do things without thinking about consequences, you might damage your system and lose data. The solution to this problem is usually very simple. Your hard drive might have disk errors, therefore you are not able to start your system. This often happens when you restart your PC during a boot-up sequence while it’s loading safe-mode for example.

1. Step Find your Windows DVD that you used to install Windows 7,8 or 8.1

2. Step Start your PC, insert your Windows DVD and hit a key when you are asked to (to boot from DVD). It is possible that you have to change the boot order in your BIOS to boot from DVD.

3. Step Follow the instructions on the screen, but don’t install Windows 7, instead click on “Repair your computer“:

The installer will now search for Windows installations on your PC and list them all. Select your Windows 7 installation and click on next.

4. Step Open the command prompt.

Attention: Do NOT click on “System Restore” or “System Image Recovery”. If you try to restore/recover your system that way, you might damage your Windows 7 installation irreversibly.

5.You will probably be in a folder X:\sources\ . Don’t worry, if your partitions are still there you can run a chkdsk on them.

Run a chkdsk for your main partition (e.g. C:), to do that enter:

chkdsk c: /f/r

/f /r will both fix errors and recover lost data.

/f will only fix errors on your disk

/r will only recover lost data

This will, in most cases, repair your disk errors and you will be able to start Windows 7 again.

Windows Bootrec.exe Commands – Repair MBR

While you’re at it, you also might want to repair and fix your MBR (Master Boot Record), add a new boot sector and scan your disk for Windows 7 or Windows 8 installations.

/fixmbr

This will create a new Master Boot Record, but will not overwrite your existing partition table.

/fixboot

This will add a new boot sector. If you boot sector is damaged you might not be able to start your system.

/rebuildbcd

Scans your disk for Windows compatible installations, needed to repair your Windows 7 or 8 installation. If you can’t find any bootable Windows installations, also try using the command bootrec /ScanOs

If you still can’t fix the problem, try to run chkdsk until all errors on the disk are fixed and it won’t say “X:”. You need to be on partition C or D, depending on where you installed Windows. If that doesn’t work for you, you should try to find a way to get to C first. Executing on X won’t help to fix the issues

I’m Stuck In X:\sources\, Help!

No worries, that’s alright. X is a system-reserved partition that aids you with the recovery, so if you see the X:\sources and not C:\ don’t worry and follow the instructions above.

Please always make sure to remove additional hard drives or USB sticks are currently plugged into your PC, you may be booting from a corrupt (external) drive and wouldn’t even know it or you may be booting from a stick that isn’t even bootable and then you’d also receive the error “missing operating system”