RHEL installation made Windows unbootable

I just installed RHEL 6.10 on my workstation, which also run MS Windows 8.1. Unfortunately, the installation rendered my Windows unbootable. I need help to fix the problem; any helpful suggestions you can give are most appreciated.

I don't have fancy disks (like LVM or SCSI); I have a single disk with 28 partitions (GPT). The C:\ drive for Windows is on /dev/sda5, so that's the address I gave the bootloader for the other OS to boot. When my machine starts, the bootloder menu shows the WinOS option along with RHEL, but when I select it, I get the error message: "EFI path must be a full path, or ...". Then I checked the config file /boot/efi/EFI/redhat/grub.conf, and it looks reasonable. Here is what it says:
title WinOS
rootnoverify (hd0,4)
chainloader +1

Much thanks in advance, if you can help.