20 gig harddrive. With the software that came with your drive, partition it into 3 equal drives. The program will set the bootable partition.
Install Win98 just as you always have...
Install W2K from within '98. It will give you an option to specify the partition to use. In this case 'C:' is the '98. Choose 'D:' for the W2K install. Choose Fat32 for best compatibility.
Thw W2K installation program will do the rest...no need to start discussing extended, logical, etc. Just let the installation program do it's stuff.