In November of last year I tried installing Vista to a second drive on my XP box. Bear in mind, I was careful to add a drive such that it came before the Windows XP drive in terms of the BIOS enumeration of disks, so that the Vista release candidate wouldn’t have any reason to touch that drive whatsoever…
Of course, Vista detected the XP install and offered it to me as a dual boot option. Very nice.
However, despite my care in trying to ensure the drive was safe from Vista, when I unplugged the Vista disk and tried to boot XP, the drive wouldn’t boot. The error I get: “A disk read error has occurred. Press ctrl+alt+del to reboot”.
I’ve tried booting my XP SP2 disk and running fixboot c: and fixmbr c:, I still get the same error. I’ve tried copying the ntldr, etc, from a working XP drive to see if that would fix it, still no dice. In order to boot from the XP install, I have to keep my old PATA drive, that I used to have Vista on. That brings up the Vista boot selector and then XP boots off the SATA drive.
I’ll try a Linux recovery disk and see what fdisk says about the partitions: maybe Microsoft’s “active” isn’t the same as “bootable”?