Grub doesn't include other HD in list

Sat May 22 00:25:31 UTC 2010

>
> I'm on an Ubuntu 10.04 64-bit install. On one 500GB HD I have Vista  
> and 10.04. On a seperate 40GB HD I have Ubuntu 9.10 32-bit. Grub is  
> installed on the 500GB HD. But, on it's boot list, all I see are  
> 10.04 ( and it's kernels and recovery modes), memtest, and Vista. I  
> don't see any 9.10 installs. However, a "ls" command at grub command  
> prompt showed two hard drives. What's going on?