The best move to make at this point if you dont' need any more partitions on the HD is to download and install free Partition Wizard, rightclick on the XP partition, choose Modify>Convert to Primary, OK, Apply all Steps. Then follow the steps in Method Two of the tutorial.
In the future if you want to add any other partitions to the HD you'll need to convert D to Logical extended which can contain as many sub-partitions as you want. The limit for Primary partitions is four, after which you risk conversion to Dynamic Disk which you don't want.