first off you cant format while it is running ... you have to
boot to dos disk and format
easiest way boot up to windows xp pro disk ... make sure in bios u have set first boot device cd rom ...when it goes into xp you have to accept license agreement and then it will give you option to install xp and hit enter and then that screen you can delete partition and add it again or it will ask you if you want to format the partition ..I just blow partition away and then It would ask to format it for ya ..and you can decide quick or full format ...quick does it real quick just wipes drives ..full format does it all
---remember fdisk and then formatting you loose all your data so be sure you want to do it ----
I like a program called ghost ..if you format often ..like I do cause I am technician and have to test new software and stuff ..it saves you to reformat from scratch and it loads back all your programs and stuff ... just to let ya know
but those are the two ways ...
i can be contacted below if need more help