Ubuntu loads and you use the utility called diskparted which can be run from konsole or by finding the link in the shorcuts (if it is there)... if you would rather format it yourself then there are tutorials available through Ubuntu's website. As for the dual boot option, I will tell you here how to do it:
first insert ubuntu cd and let load... after the desktop loads, click the konsole (terminal) and type mount and press enter. This tells you what hard drives are mounted... look in the list for the NTFS volume, it should be /dev/hda1
get this data and type umount /dev/hda1 (or whatever your NTFS drive turned out to be) - this forces ubuntu to unmount the hard drive so you can make changes
now enter diskparted... this utility will allow you to resize your windows partition so you will have room for ubuntu
in the GUI screen, you should see all the connected hard drives, click on the one that has your NTFS, in this example, /dev/hda
now, i havent done this, but you are supposed to be able to drag the bar from the right to the left which resizes the ntfs partition.. dont go too small or xp will not have much room... once you have done this, you have to click on write changes or apply or something similar, if it is successful, it will tell you... then exit distparted and go back to the konsole screen and typr reboot causing ubuntu to reboot.
after ubuntu is reloaded again open konsole and umount /dev/hda1 or whatever the name is
now you may use diskparted to make your new linux partitions or you may use fdisk... google ubuntu dual boot and you will find resources aplenty for this action....`