1. ensure your computer boots up cdrom first and Hard drive second. this is done in the bios settings at start up by pressing the del key normally.
2. ensure Xp pro is in and boot up, when it asks you to press any key to boot from cd then do so.
3. follow on screen promps until it says to to repair xp press enter (i think) but to install a new copy press esc key.
4.press esc key and i will tell you that there is already a copy of windows installed, do you want to install any way, press enter(follow what it says on the screen). eventully it will ask you where to install the windows directory and at the bottom it should say to delete the directory press (key) do it and confirm again. once this is done your C: drive should of disappeared and it should now be unpartitioned. press c to create a new dierectory and confirm, windows will now format the drive in one of 4 ways.
5. best to fromat using NTFD format and windows will now format the new drive and automatically install it's self