Log in as root in Red Hat and type
Code:
grub-install /dev/hda
That will put Red Hat's standard boot loader Grub into the MBR, thereby overwriting the Windows MBR.
I assume your first bootable disk is hda as you may have a problem to get Red Hat serving the Sata disks anyway.
In the original installation of Red Hat Grub should have been installed and have the necessary menu.lst in /boot/grub directory. If you can't find it then we can write out for you but requiring the content of
posted here first.
If you install Windows after the Red Hat or have changed the disk order since then we may have to advise further on how to incorporate Windows as a booting choice in Red Hat. For that we need to see the content of your /boot/grub/menu.lst.