Firslt, NTFs is a total no-go. Don't even think abt it. FAT 32 is the standard and stick to it unless you "reaaaalllllyy" need NTFS. I don't see why would you need NTFS. Anyways, moving on, first install XP on c: (fat32). Then, do setup of Windows 2k. You would find a checkbox "Let me choose drive partition" which you must enable. See, it is not necessary that you install 2k and XP on different partitions, but it would be better because otherwise it would be sharing the same program files folder. The problem in this is that within program files, you have accesories, common files, some dlls which would be different for different versions of Windows and some programs then might stop working on XP (like for eg, when I installed 2k on 98 in c:, I was unable to use msconfig, mspaint etc). For stability issues, choose different partitions, even if that may mean you would have to install applications twice. You needn't install games twice. Most games would work (if you want help on how to make games work in both the windows without installing them twice, I'll let you know)
Regarding dual boot options, XP or for that matter 2K give excellent options automatically when you try installing different versions of Windows which could be accessed from the control panel.
For knowledge sake, to partition in NTFS, when you do setup and it then boots into DOS, after you choose your partition, setup would ask whether you want to convert it to a NTFS partition.