My experience in dual booting windows OS and linux is that never overwrite windows bootloader with grub.When installing linux on a separate partition it does give an option to either install grub on same partition as your linux install or entire disk which clearly overwrites windows bootloader.In first instance windows bootloader is in control and in second instance grub is in control.

If grub is in control then we can launch windows from within grub but if windows bootloader is in control then to launch linux you need to install EasyBCD and add linux entry there.