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 only means that either my disk has some small disk errors or my master boot record is damaged.
Run chkdsk to repair disk errors
1. Step Find your Windows 7 DVD.
2. Step Start your PC, insert your Windows 7 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 7 Bootrec.exe – 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 installations.
This will create a new Master Boot Record, but will not overwrite your exisiting partition table.
This will add a new boot sector. If you boot sector is damaged you might not be able to start your system.
Scans your disk for Windows-7 compatible installations, needed to repair your Windows 7 installation.