computer cannot boot

My computer is set up dual boot with windows ME and red hat in two different hard drive.
And GRUB is my boot loader. But recently, I cannot boot from it. It shows "cannot find
operating system." Then I took out the Hard drive with red hat on, and set the "Master"
jumper for the drive with windows Me on, try to boot the windows. Problem again. It shuts
down after POST. Any help appreciated. BTW, I lost my rescue diskett. thanks