1. Is your drive partitioned? If so, follow these procedures to remove one of the partitions.
*Start > Run > type "compmgmt.msc" then click ok
*Click on "Disk Management" and wait for your computer to scan your disks
*In the right hand pane you will see each physical disk within your computer on a separate row, and each disk is displayed with it broken up into its partitions.
*After confirming which partition you wish to remove, right click on it, and select "Delete Partition" and click yes when prompted.
Please note the following:
When you delete a partition, all the data within that partition will be lost.
The partition containing Windows XP cannot be deleted from within Windows.
Extended partitions cannot be deleted unless the partition is empty – you must delete all the logical drives within it first.
2. If there is only a single partition, then try this step and see if it works:
*Start > run > type "msconfig" and go to the boot.ini tab and click "Check all boot paths" and it should detect that only one version of XP exists and delete the other one for you.
Thanks to deluxe_247 for the awesome sig.