Removing XP Home

Our company is buying Dell laptops bundled with MS XP Home ed. We are wanting to delete the installation and load Windows 2000 Pro. Booting from the W2k CD, when the option to delete existing partitions comes up, we are able to delete C:\, but unable to delete two small partitions that appearently contain XP files; after installation, XP still appears as a boot option. How can these mysterious partitions be deleted?