Before you do anything, boot the Ubuntu liveCD, and from a terminal run this and post the results (it'll give us an idea of the Vista partition table)
Code:
sudo dd if=/dev/sda skip=446 count=66 bs=1 | hexdump -C | less
After that, you can scrub the disk like this (zero first 100 sectors - nothing scientific)
Code:
sudo dd if=/dev/zero of=/dev/sda count=100
It appears Vista allocates partitions differently than everyone else - including XP. Allocate your partitions from Ububtu liveCD, then do the Vista install.
(presumes /dev/sda as your disk - it may be /dev/hda)