After much trial and error, here's what I found that works. This will be installing Vista/XP/Ubuntu 7.04/XP in that order.
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I hope this helps at least one person out, whether it be a clearer understanding of partitions or booting. I know I broke it down shotgun style, but wanted to leave as little room for question as possible.
You most certainly have!
Great work, Slappy, I'm sure a lot of people will benefit from this - probably the most step-by-step EasyBCD-related guide I've seen so far!
Glad you got it to work, too