I'm on archlinux so maybe it's different for you:
Here is file at
/etc/grub.d/40_custom which manages Windows boot entry
Code:
#!/bin/sh
exec tail -n +3 $0
# This file provides an easy way to add custom menu entries. Simply type the
# menu entries you want to add after this comment. Be careful not to change
# the 'exec tail' line above.
menuentry 'Windows 8' {
insmod part_msdos
insmod ntfs
set root='hd0,msdos3'
parttool (hd0,msdos3) boot+
drivemap -s (hd0) ${root}
chainloader +1
}
Please note that
msdos3 is the Windows partition, I don't have
System Reserved partition. You may want to set that instead.
You can try to edit/create that file and run command to update grub: