And since Windows XP doesn't natively write to DVD+/- R/RW, you'd be using
third party anyway.
When you make your image, choose the option in the application to split into
multiple image files for you.
Not natively from XP at least. Some of the DVD applications will span DVDs
for you, but generally you have to either create the image in DVD-size
chunks, or split it, with third party apps. EG I use Norton's Ghost and it
lets me create the images in 4.4 Gig separate files and can reassemble them
when/if they're needed.