Using the arrow keys on your keyboard, highlight the line that says Unpartitioned space. Press C to create a partition on this unpartitioned space.
Warning Note: You may have other partitions on this drive and on other drives that may be installed in your PC. If so, you may have a number of entries here. Be careful not to remove partitions that you may be using as this will remove all data from those partitions permanently.
Please proceed to How To Clean Install Windows XP (Part 2 of 4) to continue.