I have a multiboot system where legacy Grub is installed in MBR and the root partition of opensuse 12.1. This has been working well until now. I can boot into Windows, Ubuntu, Fedora 16 Gnome and Fedora 16 KDE:
Here's part of opensuse's /boot/grub/menu.lst:
title Fedora 16 KDE (/dev/sda10)
title Fedora 16 GNOME (/dev/sda12)
I just installed F17 RC3 into the root partition of the same existing /dev/sda10 of F16 KDE and during installation placed bootloader (Grub) in the boot/root partition of /dev/sda10.
When installation is completed, I rebooted into F17 but got Grub Error 15 (File Not Found). I don't understand why, because I did the same thing, i.e. placed bootloader (Grub) in the root partitions when I installed F16 KDE and F16 GNOME.