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Windows 7: Missing Operating System Windows 7

29 Aug 2010   #1

Windows 7 Ultimate x64
Missing Operating System Windows 7

I am getting the "Missing Operating System" message on boot. Here is the strange thing...if I change the boot order in the BIOS and have CDROM first and choose not to boot off of it Windows 7 loads fine. If I put HARDDISK first then I get the missing operating system message. I have tried running CHKDSK, BOOTREC and the plain old Windows repair util. None of them have worked.

Anyone have any ideas?

My System SpecsSystem Spec
29 Aug 2010   #2

Windows 8.1 Pro RTM x64

Hi kansasjhawk and welcome to Windows 7 Forums

That's a strange one.

Normally, if you have a bootable OS disk in the drive, and the drive is higher up in the boot order set in the BIOS than the HDD, then a message will appear asking if you want to boot from the drive, and to press any key if you do, failing which booting will continue with the next device in the boot order. The actual order doesn't matter normally, unless you specifically need to boot from floppy or CD/DVD.

Just out of interest, what interface do your HDD and optical drive use (PATA/IDE or SATA)?
My System SpecsSystem Spec
29 Aug 2010   #3
Microsoft MVP


Boot the Win7 DVD Repair console or Repair CD, make sure Win7 partition is marked Active: Partition - Mark as Active

Now boot back into DVD Repair console or Repair CD, click through to Startup Repair to run up to 3 separate times to repair or rewrite the MBR to Win7 partition: Startup Repair - Run 3 Separate Times
My System SpecsSystem Spec

29 Aug 2010   #4

Windows 7 Ultimate x64

Fixed it. I just had to restore the BIOS defaults...even though all I had changed was the boot order. As long as it is fixed.....
My System SpecsSystem Spec
29 Aug 2010   #5
Bare Foot Kid
Microsoft MVP

W 7 64-bit Ultimate

Thanks for the update, your info may help someone else.
My System SpecsSystem Spec

 Missing Operating System Windows 7

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