I used to have an OS installed on sdb but for some reason it wouldn't boot wouldn't work unless I changed hd(1,1) to hd(0,1) though your computer might be different. You'll probably have to guess/check by hitting e in the grub menu and editing the parameters at boot. Once you find something that works, you can change it permanently in your OS.
I would personally just backup your menu.lst file, then run SuperGrub. It's a bootable disk that does a really good job of finding OSs and setting up Grub.