Need Advice. Can I install an xp dual boot over dell recovery partition area?

I have run into my first problem with vista. My old music hardware (synths and keyboards and stuff) is not compatible with vista and the company has stated they will not be supporting them in vista. I kinda like vista though, so I want to have a dual boot. The thing is, I've already installed all my apps and copies some files over, so... do I have to reformat everything and start again,
OR
can I clear the dell partition (but keep the partition there) and use that area to install xp? If this is possible, how to do you do that? How do you delete all the data from a partition and install xp in it? I hope this is possible...
Is there a negative side to doing what I'm suggesting?

I really need some advice soon, cause I have a presentation for uni soon and I need to get that music gear up and running again so I can create something in time. I will only be using XP for when I want to do music stuff, I won't be installing a whole bunch of stuff in xp.

On an extra note, can the same program be installed in both OS? Do they take up twice as much HD space that way? What's the deal? :| Anyway to get them into both registries without having to install in 2 seperate places?

Any help would be much appreciated!

 

Oh, also, how much space will be required for an xp partition if I don't install programs into it?