You need to reinstall?
NOTE: formatting your hard drive will delete all files to backup your data first.
Put your CD into your computer and turn on the computer - It should say "Press any key to boot from the CD..."
If it doesnt do this then either the computer isnt set to boot to CD first or your CD isnt working.
Once it boots to the CD, press enter on the first screen when it prompts.
press F8 to agree to T & C's
Delete all partitions you see (pressing D and L to confirm normally)
Press enter to install on the unallocated space
do a quick format and let it install.
you will then need to run through the first time user setup.
***Make sure you have a valid XP product key otherwise you cannot install.