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If you have damaged the boot sector of one of your partitions (e.g. by installing GRUB in it by mistake), you may have troubles. For example, if it is a Windows partition, you will not be able to boot into Windows any more.
Remark: if you have this problem, Boot-Repair should automatically warn and tell you the name (eg sda2) of the broken partition.
Here is how to repair it:
Via an Ubuntu disc
Step 1 - Boot on a liveCD or liveUSB
Boot your computer on a Ubuntu live-CD or live-USB, then choose "Try Ubuntu".
Step 2 - Install TestDisk in the live-session
Once in the Ubuntu live session, install TestDisk this way:
- Connect internet
Open the Software Center, in the top bar click Edit -> Software Sources -> enable the Universe repository
- Open a terminal (Ctrl+Alt+T) and type :
sudo apt-get update
sudo apt-get install -y testdisk && sudo testdisk
Step 3 - Use TestDisk
- Via the arrows and the Enter key, go to the [No log] menu,
- then select the disk where the broken partition is,
- then select [Proceed],
- then choose the type of partition (generally [Intel]),
- then select the broken partition with [Boot], it will display something like :
Boot sector Status: Bad Backup boot sector Status: OK Sectors are not identical. A valid NTFS Boot sector must be present in order to access any data; even if the partition is not bootable. [ List ] [Backup BS] [Rebuild BS] [ Dump ]
7. Check that you have "Status ok" below "Backup boot sector"
8. select [Backup BS].
Via a Windows disc
This method is only able to fix the bootsector of a Windows partition.
1. Get a Windows recovery disk, as explained on this page
2. Boot on it, and use the 'fixboot' command (not the 'fixmbr' one). This should fix the bootsector of Windows.
Discussion thread on ubuntuforums for any question/comment about this tutorial. (this is not a thread for support, if you need help please create your new own thread here)