Can I Vista->new partition->XP->copy programs??

Here’s where I am and what I’d like to do:

Where I Am:

I was a happy XP user and installed Vista Premium the day it was available.
Since that time I have spent tens, maybe hundreds, of hours trying to get
some of my hardware and software to work properly. 95% of everything now
works after installing new drivers/updates, and replacement software, but the
remaining part contains software/hardware that I really need and can’t get
Vista replacements for.

I am close to throwing in the towel and reverting back to XP, but I like the
Vista environment and don’t want to lose the time and money spent to get to
where I am now. I believe that Vista will ultimately solve my remaining
problems in a future SP but I need to move on now.

My machine:

I have a Dell E-510 that came with Windows XP Media Edition preinstalled. I
have 3 large HDDs and a DVD-RAM burner. I also have a 120GB external USB HDD.

What I’d like to Do

I would like to somehow boot into either XP or Vista and use my choice of an
OS with all of my programs installed. I don’t know whether this means an
additional partition on my C:\ drive or whether installing the OS on a
different drive makes more sense. Because my XP came preinstalled, I have
the Dell “Restore� CD but not a Microsoft XP install CD. (actually – I have
an XP install CD but that copy of XP is on an older/slower machine that I
need to keep operable, and I think XP can be installed on only one computer).
After I have the two OS configuration, I think that I can probably use the
Vista file transfer utility to move my files to the newly created XP
partition (maybe using my external HDD), right?

Though I never have imaged my HDD or created a dual boot partition, I think
that I have the expertise to do it. What I need to know is where to find the
self-help needed. I’m using MS OneCare for my firewall/AV protection if that
makes a difference (it has created problems with other software
interactions). I’m not beyond purchasing software to do the work, but I’d
rather do it myself if possible. I just need first to know if it’s doable,
and then some good instructions on how to go about it. If there is a book
that I can purchase to walk me through the process, I’d buy it, but a Google
search hasn’t found anything that appears appropriate.

Thanks greatly.