Vista - Problems with Dual Boot in RC1

I have been running an XP/Vista dual boot for sometime, and today I installed
the latest RC1 release.

Install went ok, but when I rebooted it went straight to Vista - no bootup
choices for XP. I have two physical drives - Drive 0 has two partitions for
XP and Vista. Drive 1 is just for data. Prior to the RC1 update when booting
to Vista, it correctly assigned letter C for the main drive, D for the
(logical) XP drive, and G for the data drive.

Now, however, it insists on assigning the data drive as drive D, and
apparently the dual boot manager only scans drives C and D to try and find
Window versions. Thus, it never looks at the XP partition and therefore boots
directly to Vista.

I have tried to change the drive letter in Vista under disk management, but
it won't let me reassign drive D as it calls it a "system" disk. If I
physically disconnect the data drive, everything works and I can get the dual
boot options as usual.

I have booted with the data drive disconnected, and then connected the drive
when I get to the boot choice screen. Vista then assigns that data drive as
drive G. But if I reboot, it's back to direct boot to Vista.

Other things I have tried

1. Reinstalling Vista with the data drive disconnected. It works, but once
the drive gets reconnected, same old problems.

2. Removing the bootmgr files from the data drive - doesn't work, I get an
error message saying that Bootmgr file is missing.

3. Using Vista "repair start" option from the install disc fails to even see
XP.

Any solutions to this? Vista has an application called bcdedit, but it won't
run from the command line. How do I get Vista to stop looking at the data
drive as a system drive, or otherwise get the boot manager to recognize the
presence of XP?