You can't install XP "into" Windows 2000. You can, however, install XP over it, thereby reformatting the disk and erasing Win2K. You can also set up a dual-boot setup and have both operating systems on one machine. You must meet system requirements for each operating sytem. The easiest way I know to do this is get a copy of Partition Magic, I think Symantec owns it now. It comes with Boot Magic, which makes setting up a dual boot system as easy as it can be. There are other ways that more knowledgeable people might know.