Comment 5 for bug 98757

Olivier, the problem is that during installation, the SATA drives were detected (by the kernel) first (hd0, hd1) and your IDE drives became hd2, hd3, hd4, hd5. The Linux drive hd3 (the 4th) was therefore stored in menu.lst. Now when grub is starting up, reading hd3 from menu.lst, it asks the BIOS for the 4th hard drive, but the BIOS starts with the IDE disks, so your Linux disk is the 2nd drive now.

It's difficult for the installer (only seeing drives through the kernel, without using BIOS) to guess in what order the BIOS will present the drives.