When you installed Ubuntu, there should have been some options for where to install grub...one way to proceed is simply re-install and watch for this. If there is any doubt, tell it to put grub on a floppy.
Another option: if you can get to a terminal (live CD, or by pressing ctrl-alt-F1 after the install CD has booted), you can install grub. Let's assume that drive 1 is the 1st SATA, drive 2 is the 2nd SATA, and that Linux is on one (/) partition on drive 2:
grub starts the grub shell
root (hd1,0) points grub at the "home-base"--defined as the location of the /boot directory
setup (hd0) puts grub on the mbr of drive 1
Now, you need to check the grub config file: /boot/grub/menu.lst
To do this, you will need to mount drive 2 to the filesystem being used by the liveCD/installer.
mount /dev/sdb1 drive2
cd drive 2
Here you should see the root directory of the Ubuntu install. Now to get to the Ubuntu boot/grub, do:
cd boot/grub (do NOT put / in front of the boot)
you should see a file named menu.lst (or possibly grub.conf) Open this with an editor--eg nano--and look for an entry similar to this:
kernel /boot/vmlinuz<something> root=/dev/sdb1
The entries for kernel and initrd need to match the names of the files in boot. On easy way to proceed is to create soft links in boot named simply "vmlinuz" and "initrd". Then you can use these generic names in the grub config file.