Windows XP, ME and some versions of windows 98 CD has a bootup feature. You will have to have it enabled in your bios which most of the time it usually is, by default. Pop the CD in as KeyMastur mentioned, and you computer (depending on the type and model) may ask you to press any key to boot from CD, press any key, and the system will boot up. IN the process of the startup of the CD, XP will allow you to delete an existing partician. If memory serves, one must press the d key then the L key to confirm deletion of the existing partician. Once the partician is deleted, then it will take you back to a screen that will say "unparticianed drive" or something like that. At this point your data is gone. then press the C key to create a new partician, it will ask you the size you want to make it. I usually go with the default, the maximum size of the drive, unless I want to break up a partician for some security or file reasons. ONce that is done, then it will instruct you to format, (I usually choose the "quick" format") . After the format is finished, the Operating system in this case XP will proceed to install.
This is probally the easiest way to fdisk and format a hard drive. There is another way with a windows 98, ME or XP start up disk. If you know how to use the fdisk command and delete a non dos partician (if it is NTFS), and create a new one, then you have to go back and format the drive. Okay I am off the subject, didn't mean to confuse you. Really hard to tell someone how to do something over a thread you know what I mean.
If I confused you just simply follow the instructions from the bootup CD they are very easy to understand.