This article will show you how to fix the problem of grub not showing existing windows partitions after installation of CentOS 7.
The problem is, that CentOS seems not to be able to detect the bootable ntfs partitions without installation of some extra software. You will need the ntfs-3g tools. Do get this you need to enable the EPEL repository first. Do so by running the following commands:
wget http://dl.fedoraproject.org/pub/epel/7/x86_64/e/epel-release-7-5.noarch.rpm rpm -ivh epel-release-7-5.noarch.rpm
Then install the ntfs-3g tools by running this:
yum install ntfs-3g
If you have done this you can try to automatically generate the grub2 configuration file and check if os-probe detects the partitions (it should normally do so)
Copy the output into the grub2 configuration file on your harddrive. By default this file should be located here:
If you saved the file you can try to reboot. The missing Windows partitions should now be bootable from the grub menu. Alternatively to this way you can also add the entries manually. There are several hints on how to do this on the internet.
Visit the following links for further information: