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I used hp recovery manager to install Windows 7. I previously had Ubuntu 11.10 installed. Now when I boot I get a grub rescue prompt and error:unknown filesystem. Does anyone know how to fix this? Thanks.

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up vote 3 down vote accepted
  1. If windows 7 is installed in the same partition where ubuntu was previously installed then there is no way to rescue ubuntu. If you do not want to use ubuntu and continue to use win7 only then you can restore windows boot manager using windows installation dvd. Follow instructions after booting from windows dvd.

  2. If windows and ubuntu are installed in separate partitions you can easily revive grub boot manager using a ubuntu live system. The internet has a lot info how to do that.

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If you had both Windows and Ubuntu side by side, maybe you've hit the same problem as I did. I got it fixed by changing my fstab file and rewriting the partition table through Testdisk, see my thread here

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Ubuntu has a help page devoted to this particular issue:

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When you install Ubuntu then the then the Windows bootloader is replaced by Ubuntu grub. To access the Ubuntu and the Windows you have to reinstall the grub. See the grub rescue method to reinstall the grub

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Whilst this may theoretically answer the question, it would be preferable to include the essential parts of the answer here, and provide the link for reference. – Mahesh Nov 12 '12 at 7:18

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