Vista and XP booting

I recently did a hard drive upgrade, which has left me with a somewhat strange
situation, whereby I can boot XP, and not Vista, or Vista, and not XP.

Right now, XP is booting, with no boot manager menu.

If I boot the Vista DVD and do an automated repair, it replaces the boot
sector with its boot manager, and I'm able to boot Vista. But then it fails
to boot XP, saying that \ntldr can't be found.

To boot XP, then, I have to boot the XP CD, and replace the boot sector, which
kills the Vista BM, removing my ability to boot that S.

Any pointers on what I might do to correct the Vista boot manager so it's
capable of booting XP?

And now, so I can vent a bit about my ordeal (which has lasted for several
days), here's the backstory.

This is what I started with:

Drive 0 - Windows Dynamic, 250GB
50GB - C:, Windows XP
200GB - E:, Stripe Part 1
Drive 1 - Windows Dynamic, 250GB
50GB - D:, Vista
200GB - E:, Stripe Part 2
Drive 2 - Windows Dynamic, 750GB
750GB - F:, Stripe Part 1
Drive 3 - Windows Dynamic, 750GB
750GB - F:, Stripe Part 2

That setup was working fine. I was getting a bit low on space, though, so I
bought a pair of 1TB drives, with the goal of ending up with this
configuration:

Drive 0 - Windows Dynamic, 750GB
150GB - C:, Windows XP
600GB - E:, Stripe Part 1
Drive 1 - Windows Dynamic, 750GB
150GB - D:, Vista
600GB - E:, Stripe Part 2
Drive 2 - Windows Dynamic, 1TB
1TB - F:, Stripe Part 1
Drive 3 - Windows Dynamic, 1TB
1TB - F:, Stripe Part 2

I had no issues with the 1TB drives, other than the fact that moving over a TB
of data takes a fair amount of time. Since I had two spare SATA ports, I did
that part before messing with the Windows installations.

So then I use Norton Ghost 14.0 to copy the partition data from C: and D: to
their intended new homes.

I actually got XP to boot once, but on the first reboot, it failed with some
complaint about lsass.exe, after which it promptly rebooted. This would
happen repeatedly.

Vista may have worked at that point, if I booted from the DVD and did a
repair, but I wasn't interested in that until I got XP working (where
everything is installed - Vista was a clean install, because it failed to do
an upgrade on a copy of my XP install).

So I plug the 250GB drive with XP back in, boot from that without a problem,
and try various ways to backup/restore to the new drive. ASR worked, but
insisted on making the same-sized partition, and there's no way I know of to
resize a Windows dynamic boot volume.

I eventually downloaded a GParted live CD, from which I was able to copy both
the XP and Vista partitions to their new homes, resized appropriately. XP
decided it was booting from drive E: for some reason, so it didn't work
immediately, but I was able to get Vista to boot by doing an automated repair
from the DVD. From there, I modified the XP registry to assign the correct
drive to C:, and XP booted.

So there I was, with both XP and Vista booting. But on "Basic" discs, where I
needed "Dynamic", so I could stripe the remaining space into a larger volume.

So I converted both drives to dynamic in XP, which itself booted just fine
afterwards. Vista, however, threw a BSD on startup, and could not repair
itself from a DVD boot.

I then deleted the Vista volume, and repeated the GParted restore, which left
XP still booting (from a dynamic drive), and Vista booting from a basic drive.
In Vista, I converted its drive to dynamic, and created the striped volume
from that and the already-dynamic XP boot drive.

Which caused XP to throw a BSD on startup.

I started over, copying both partitions with GParted, and this time first
converted XP's drive to dynamic while in XP, and then Vista's drive to dynamic
while in Vista, without creating a striped volume.

Rebooted into XP, and it sees the Vista drive as a foreign dynamic volume. Can
you guess what happened next? Yes, it failed to import it.

So, I gave up on that idea, since the only workable way I could think of to
achieve it would be to wipe out Vista and install it from scratch, after all
the volumes are defined.

That meant adding one 250GB drive back to the system (which will come back to
bite me later if I buy another 8800 GTX for SLI, due to the fact that the
drive tray it sits in would obstruct the full-length card - the Antec P180
case is about 6mm too short, front to back). I figure I'll divide the drive
into 125GB partitions, with XP on one, and Vista on the other.

That's what brought me to where I am now.

You need to use a utility like EasyBCD here is a good link that covers both scenarios of which Os is loaded first http://apcmag.com/how_to_dualboot_vista_with_xp__stepbystep_guide_wi th_screenshots.htm