If you use the XP cd, go into the bios, set it to boot from the CD and then follow instructions. You can format in either FAT32 or NTFS.
If you are doing it from a boot disk, make sure you have the bios set to boot from the A: drive and then once in A: type... format c: /u There is a space between c: and /u and you can only format in FAT32.
This will do a check of you HDD and a complete and thorough format. Once that is done, you will need to go back into the bios and change it to boot from the CD.