Dual boot Windows 8.1 Pro and Fedora 20

[GervanDijck]

Hello everybody ,

I have a problem :

Laptop Dell 17 R model 3721 ,disk 1Tb , mem 8 Gb , vga : Radeon 8730 m and
Intel 4000 hd.

I did fresh install Windows 8.1. Pro : No problems everyting runs fine.

Therafter I did fresh install  Fedora 20 (Mate , all groups) : Runs
perfectly fine , but when rebooting , Windows 8.1 Pro does not appear in
the GRUB boot menu.

So I did run grub2-mkconfig -o /boot/grub2/grub.cfg and rebooted : No
Windows 8.1 Pro displayed in GRUB display.
After updating Fedora 20 and having a new version of the kernel , I did
run grub2-config etc. and rebooted : No Windows 8.1 dispayed in GRUB
display.

Looking in grub.cfg shows to me , that the menutree for the two kernel
versions and fedora rescue is correct generated.

Setting Bios , Uefi is a.f.: boot mode set to legacy , secure boot off.
                                load legacy option ROM.
                                boot list option legacy.

Disk layout         is a.f.:


Fedora 20
---------
DATA  : /home                322,28  Gb
           fedora home
           bios boot               1    Mb
           sda 6

SYSTEM: /boot                 500    Mb
           sda 8
           /                      51,2  Mb
           fedora root
           swap                   2,44  Mb
           fedora swap


Windows 8.1 Pro
---------------
           sda1 ntfs              300   Mb
           sda2 efi syspartition  100   Mb
           sda3 unknown           128   Mb
           sda4 ntfs             199,47 Mb
           sda5 ntfs             376,93 Gb
           sda6 bios boot           1   Mb
           sda7 ext4              500   Mb

Question : How can I manage ,that Windows 8.1 Pro appears in the GRUB boot  
menu , so I can not only boot Fedora 20 , but also Windows 8.1 Pro ?


Begging for help ,


Ger van Dijck.