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I am running windows eight alongside Ubuntu 12.04 , using the default GNU Grub (Ubuntu loads first then i used to choose Windows 8 from the list).

The computer was running normally, until just now, I booted it up and tried starting windows eight. It gives the following error:

operating system not found, try disconnecting disks that may contain an OS. 

Note that I was not trying to install/uninstall/repair anything, I just tried to start Windows 8 from grub and it gave the error.

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I've had this before (only in Vista and 7), usually for me it falls to one of the following:

Firstly check that the windows partition can be mounted in Ubuntu.

My Fixes:

1) Windows boot loader is wonky, need to do a Windows Repair from the windows disk (then fix grub one windows boot again). This should also tell you if windows is still on the disk and it hasn't actually gone.

2) grub isn't pointing to it correctly, which I've fixed before in 2 ways:

2a) (easier and faster)

2b) (WAY more options and automatic but took an entire ice age)

Hope this is helpful.

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Thank you very much for the input. – Usman Shah Oct 15 '13 at 18:06

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