grep menuentry /boot/grub2/grub.cfg
This will display all your grub entries
Highlight the entry you want to default to - for example Windows 7 (loader) (on /dev/sda1) Right click and choose copy
Change the entry
GRUB_DEFAULT="Windows 7 (loader) (on /dev/sda1)"
i.e. paste the entry you want (including the quotes)
Save, then type
PS: Having this "Windows 7 (loader) (on /dev/sda1)" is enough.
grub2-mkconfig -o /boot/grub2/grub.cfg
thats it and this worked for me.