lol, you cant format your hdd when you have booted into windows as it would eventually delete the files it needs to operate and would have to shut down half way through the format, if you can see what I mean?

Formating a windows xp hdd isnt quite the same as doing it with win98, where as with win 98 you would boot from the start up floppy disc and then type format c: , in win xp you need to boot your system up from the win xp CD.

Check in your bios under boot option (or something similar) and make sure you are booting from the CD ROM first.

Once you have ensured this put the win xp disc in and restart your computer. You will get a screen asking you to press "R" to enter the recovery console or press enter to install windows //press enter here if you want to format and start afresh.
Next it will show you a list of any partitions you have and ask where you want windows to go, select your primary partition //usually C.

It will then ask you "are you sure you want to install here (or words to that effect) if so press "C" to continue. Press C.

It will then warn you that having multiple O/S's on the same partition aint a good idea......... do you want to format? if so press "F". Press F.

It will do the rest by itself, the next thing you will have to do is choose your country, time zone etc etc.

happy fdisk'in ;-)