message GRUB - no boot. Help

[Francois Massonneau]

Hi,
This morning, suddenly, after many years without a problem, my system doesn't 
want to boot.
My system is full SCSI, and I run FC3 (I did an upgrade from FC2 to  FC3).

Now, when I power on, after the disks checking by the Adaptec SCSI card, the 
only message I have is "GRUB", and the system stays that way, with a 
continuous noise.
I've started with the FC3 first install disk in rescue mode, and I can browse 
thru the directories, but I don't know how to repare that grub loader, and 
make my system to work again, as before.
Thank you for your help. Francois