I have two hard drives:

(hd0) /dev/sda openSUSE 10.2
(hd1) /dev/hda Windows XP Pro

I have GRUB installed on (hd0) and it correctly boots into both OSs.

When YaST edits bootloader configuration (such as after a kernel update) it erases the bootloader on (hd0) and installs one on (hd1)

I can fix this each time by reinstalling GRUB on (hd0) with a recue disk.

But how can I tell YaST that the bootloader should be on (hd0) and NOT (hd1)?

Edit: Even when (hd1) is unplugged, YaST still erases the bootloader on (hd0), leaving no bootloader at all!

Edit 2: If it is any help, it doesn't add/delete bootloaders when I select "Other > Edit Configuration Files" on the bottom right and edit them directly. It only add/deletes my bootloader when I make edits using the GUI, for eg, set Windows as my default GRUB menu item.

Yast - System - Bootloader configuration - Edit configuration file. Try to edit 'Replace code in MBR'; set it to 'Leave untouched', or whatever option 10.2 offers that means the same thing.