Partitioning is a fairly simple concept. As long as you understand there is so much room on a hard drive, then its easy. We will use a giant cabinet for example. Say you have 2 things you want to put in your cabinet but you dont want the two seperated. So, you take a giant spacer, and your giant cabinet has become 2 smaller cabinets. Thats basically how partitioning works. The 2 sizes of the 2 partitions can only equal the total size of the whole hard drives.
Now there are many ways to go about partitioning your hard drive. You can use programs like Partition Magic that do it for you, you just decide what you want the two sizes to be and it will split them up for you. Now if you dont want to go out and waste money on a program like that when you probably already have a Windows XP CD. If you just select boot to CD-Rom in your bios, you can boot to the XP disc and start running setup, and you can create windows partitions using their own little program Microsoft bundles in there for you.