Hard Drives Disconnect Automatic

I have a strange one. Running W2K with three IDE hard drives. About every 6 hours I hear a “Click” then a messages pop up that say I have removed my drive D & E. They are gone. The only way to get them back is shut down, unplug them, reboot with only the drive c, shut down and reconnect them and every thing is fine for about 6 hours. Any help would be appreciated.

Scott