First you need to decide how much space you need for each OS, and if you need Linux to be able to write to the Windows partitions (Linux can pretty easily read from NTFS partitions but not write...it can read and write fine from FAT32 though).
You could perhaps have a10gig partition for Linux, a 512MB or so partition for the Linux Swap, a 2gig for Win2k, a 2gig for WinXP, and the rest formatted FAT32 so all three OS\'s can use it (install programs there to share between win2k and winxp, keep mp3\'s there so all three OS\'s can play them, etc.). I would probably partition the drive first, have the 10gig (or whatever you choose) partition for Linux at the front of the drive. Install Win2k first, then WinXP. Lastly install Linux, LILO has always found my WinNT/2k/XP installs and configured everything for me.
Just a rough suggestion.