For Link #7, there's nothing but a quote saying that the forum isn't for troubleshooting issues, but development issues. So the link has no info. for dual booting.
As far as dual booting with XP Pro and Vista, that's pretty simple. You just need to resize your exisitng hdd and partition it. I've done this before and currently have the setup like that. I used 25gb for my Vista partition. I'd say atleast 20gb should be good enough or even more if you have a bigger hdd.
For the partition, download this utility:
GParted Live Disc
If you need help on using the software, their site provides very detailed and robust info. that you can follow along.
When you're done resizing and partitioning so that the drive is recognized in your "My Computer." Put in your Vista disc into your drive and it should automatically autostart. Don't do this from bootup tho, do it within Windows. Eventually, after you enter the key and everything, it'll let you select which partition to install it on. Then of course you just choose to install it onto the newly created partition you made.