If you really want to get a fresh start, please listen and follow closely...
This will only work if you have another computer in your house, or use a friends computer.With that in mind, let's begin..
Step.1=remove your main hard drive.
Step.2=look at the back of your hard drive to the left of where the IDE cable connects, you should find a set of three jumpers(pin pairs)Master, Slave, and Cable Select.Yours will probably be on Master.
Step.3=Switch the jumper to the slave setting.
Step.4=temporarilly install the HDD in some other computer(house, or friends, doesn't matter which)
Step.5=boot up the computer in which you temporarilly installed the HDD.
Step.6=go to My Computer and select the New HDD(it ussually keeps the same name you gave it, if you did)
Step.7=right click on the newly installed HDD and select format, then format the drive(do not use the quick format option, though it might be tempting)
Step.8=after formating is complete, remove the HDD again and set the jumper back to Master(or whatever it was before you reformatted)
Step.9=mount it back in your computer, connect all cables(correctly)and reboot.
Step.10=after your BIOS boots, you will see a message saying"press any key to continue booting"ignore this(for now) place your XP install disk in the disk tray and reboot again. From there it's pretty easy, just follow the steps on the screen.