That is the message you get if the system can't find an MBR. For example, I wiped out the NT installations on some computers at work before we sold them. That is the exact message I got. You might have elected to write the MBR to a partition instead of the device.
Booting to a rescue disk and using the grub-install program may be able to fix it.
Grub has auto-completion, so you could instead boot up to the rescue disk ( Or your first install disk ) and use it to locate your boot partition.
Press [ESC] at the initial menu and select the option for the grub shell.
and press the tab bar. It will present you with the disks it finds. You want to end up with something liks:
Then enter "boot" and hit return to boot up. Your particular device may be different depending on how you partitioned and installed. The autocompletion will allow you to use trial and error to locate the correct device and partition that contains the /boot directory.
While running Linux then, you will need to change the boot configuration by changing the boot device to be the first disk device and not a partition.