Vista 64 bit, Vista/XP dual-booting

[d000hg]

I'm currently running XP Home on my Fujitsu Scaleo P, which has an Athlon 64 X2 3800+ CPU. I'm getting a Vista license (both 32 and 64 bit versions) as part of a package I'm buying and I'm undecided whether I want to use it. I use my PC for my work, which is basically programming.

So a few questions:

1)Does the 64 in my CPU name mean I have a proper 64-bit PC that can run Vista 64bit?
2)Is there any particular reason why I would want to?
3)I'd quite like to keep XP on the PC. Is it easy to set up dual booting?
4)If I want dual boot, can I have XP and Vista 64bit, or only Vista 32bit?
5)Would I have to wipe my drive and start over to dual boot, or can I simply install Vista on my XP machine and end up with two installations?
6)If I end up with C:\ as XP and D:\ as Vista, will XP be able to access D:\ and Vista be able to access C:\

Thanks for your advice.