>>1
you probably have one partition dedicated to windows xp, you must first shrink this partition to make room for linux. partition magic can do this (you must 'resize' the partition which means you don't lose data), and i think kubuntu's installer can do it too (never installed kubuntu so don't know for sure)
then, in the free space, you will need to make at least two partitions, a small one for swap (make it about 1.5 * your RAM), and the rest for linux.
most linux installers can do the partitioning, and i'm not sure but most friendly ones ought to do the resize of ntfs partitions as well. (I've only messed with debian and it doesn't resize automatically so i'm not sure about others)