Difference between FIXBOOT and BOOTCFG in Recovery Console?

I have got 2 hard drives in my computer and I am getting an error that says that "NTLDR is missing..." if I switch which hard drive which is plugged into the Sata 0 port on the motherboard? I want to know how to use the newer hard drive as the readl boot disk, yet its operating system was installed later than the old drive. So, will I be able to use FIXBOOT in the Recovery Console or BOOTCFG? Any ideas?

I think that when you connect your "newer" SATA HDD to the motherboard's SATA 0 connector, either your second HDD is disconnected from the system or if it's still connected to another SATA (or IDE) connector your BIOS boot priority order indicates a *first* boot to the "newer" SATA HDD (as philo has mentioned). This is so, right?

Therefore to simplify this issue, you can try to fresh install the Windows XP operating system onto your newer Sata hard drive.