So you power up your computer to get a shocking error message:
Missing operating system
Operating system not found
An error message like that always comes as a nasty shock. But luckily it’s possible to fix it.
Why Does the Operating System Not Found Error Appear?
“Operating system not found” or “Missing operating system” error messages usually appear when users are booting their Windows Vista or Windows 7 computers. The most common reason for this error message is a corrupted operating system installation when some core Windows files are missing. If you have your Windows disc, then you won’t have a problem repairing your Windows installation.
Fixing Missing Operating System Error
To fix the “Operating system not found” error, try to insert your Windows Vista or Windows 7 DVD disc and boot from it. When the disc boots, you should get several recovery options: Startup Repair, System Restore, System Image Recovery, Windows Memory Diagnostic, and Command Prompt. You need to select the repair option and then select Open a Command Prompt Window. Now type the following commands into the Command Prompt and press Enter after each:
Make sure you get all the characters and spaces exactly right.
Now restart your computer and your Windows OS should be back to normal.
If you are having a similar problem on a Windows 8 computer, check out this Microsoft support article to take advantage of Windows Recovery Environment.