How do I remove Ubuntu and put windows XP service pack 2 back?

i installed Ubuntu on a Fujitsu-Siemens notebook. i want to take it off and put winXP back. WinXP setup doesn't recognise the hard disk. Xp service pack 3 was able to install successfully, but i want service pack two. inserting the pk 2 cd and starting installation still doesn't work. i have even tried upgrading after a windows 98 installation. still didn't work. someone help me out. thanks