If you really need to do any work to alter partitions, I strongly suggest you first back up the partitions that will be affected. Of course, that means you have to read the backup/restore chapter first.
Windows XP provides limited tools to handle partitions. A good third party tool is PartitionMagic (published by PowerQuest). It lets you create, resize, move and copy partitions. Although PartitionMagic (at least in my experience) is very reliable, it cannot guard against power fail and other hardware related problems.
As I said, back up all the important data first!