I'm not clear as to whether you wish to install Windows XP on your new harddisk or just format it.
If you are installing Windows XP you should be able to insert your CD and start your PC. Simply follow the instructions on screen.
If you wish to format a new harddisk, right-click on your My Computer icon. Select Manage. Select Disk Managment. Right-click on the block representing your new disk and select Format. Follow the instructions on screen.
Keith Mitchel, October 2005