|Are you asking about hardware requirements?|
Since XP is the newer, more resource hungry operating system then anything that meets XP system requirements will suffice for a dualboot setup with Win2K.
If you are asking how to establish a successful dualboot arrangement with XP and 2k then that is a different matter and not necessarily a question for a hardware forum.
There are several ways to go about setting up a Windows dualboot arrangement. In my opinion, each operating system should be installed in it's own partition. If you have only one physical harddrive then first partition the disk into two or more drives. Format them in NTFS. ( can be done during setup)
Next, instal the older operating system (2K) first to C
Then instal XP to a different partition. XP setup will automatically write the required dualboot startup files.
Goin' Fishin' (Some day)