I just installed Vista RC1 on a machine to demo for my club.  After
installing the larger apps, I installed ubuntu 6.10 meaning to dual boot the
machine.  Vista originally occupied the entire disk.  Ubuntu offered to
resize that partition and add the usual ones for it.  Everything seemed to
go well.  However, on rebooting there was no dual boot menu.  GRUB was set
to use a hidden menu with 3 seconds to ESCAPE before booting into ubuntu.
Looking at /boot/grub/menu.lst revealed no entry for any other OS after the
magic part of the list.  sudo fdisk -l /dev/hda revealed the expected
partitioning including the NTFS partition as /dev/hda1 although it was not
marked as bootable (I do not know if it was after the initial install).

I switched over to a similar box which dual boots XP Pro and unbuntu
6.10which works properly.  fdisk revealed essentially the same
partitioning
except that the Windows NTFS partition was marked bootable and the linux
partition was NOT.  Huh?  I do notice /boot/grub/menu.lst under the Windows
section includes a line with the "word" makeactive.

Anyway, I tried appending the other OS part of the grub menu from the box
that works to the menu.lst on the box that won't boot windows vista and just
changed the title.  But that does not work.  Next I tried booting from the
Vista CD and running its repair function but that does not work either.
There was some text in one place that led me to think Vista may be somehow
hiding a boot partition that I may have wiped out or made innaccessible.

Does anyone have any knowledge on this?

============

Oh yes, I just remembered I meant to go mark hda1 as bootable and retry
(though Vista not being able to repair makes me think that is not it).
Anyway I have to leave for an hour or so.  I'll check back in later.

-- 
Be who you are and say what you feel, because those who mind don't matter
and those who matter don't mind.  - Dr. Seuss