Ubuntu – How to manually add windows 7 to grub list

GRUB 2 is designed to be more intelligent than GRUB 1, meaning that you don't manually configure the menu anymore. Instead, GRUB now makes you solve the underlying issues that prevented it from detecting the OS, which can be a pain in the smurf.

Now, that said, there are several things that can prevent GRUB from detecting your XP drive. From my research, this usually indicates that there is something wrong with the partition itself. You should try and run chkdsk from windows or a windows repair disk. If those fail, please review the forum post below and see if you are having a similar issue. Most likely, Arch damaged a small boot partition that GRUB uses to detect the OS.

http://ubuntuforums.org/showthread.php?p=9826152

As always, back up everything prior to beginning these steps.

Good luck! Geary

Sometimes os-prober is wrong.

Look at the UUID of your Windows 10 partition, for exemple:

sudo blkid /dev/sda2

Then edit /etc/grub.d/40_custom, and at the end of the file add:

menuentry "Windows 10" --class windows --class os {
   insmod ntfs
   search --no-floppy --set=root --fs-uuid $your_uuid_here$
   ntldr /bootmgr
}

Don't forget to change the UUID.

And finally update your grub config file:

sudo update-grub

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