grub stops at the boot process

[Francois]

Hi,
This morning I wanted to fire up my computer, but I can't, the boot process 
stops at the stage where grub should have displayed the menu allowing me to 
choose the OS to start (I have one HD with linux and one with Windows).
Now, I see the command line 
   GNU Grub version 0.97 (638K lower / 3798967K upper memory)
   (Minimal BASH-like line editing is supported. etc..
   grub>
and that all.
I don't know what to do to boot. It gives me all possible commands when I 
hit tab, but i dunno what to do.
4 days ago I increased my ram from 1 gigabyte to 4 gigabytes, but it booted 
fine those last days.
Thank you for your help. Francois
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