Step by step directions - (a) if you can start from an
empty HD (without already having XP on the disk) and if the directions will work for XP

I have installed winblows 2003 and eCS on the same HD. Let us hope that if it worked for winblows 2003, it will work for XP as well.
(1) Delete all pratitions from the HD. Winblows pratitions do not create a correct partition info in MBR. Result: the eCS FDISK will refuse cooperating if it finds such partitions on your HD. Deleting the partitons could be a problem - again, bad MBR info. Tested ways: (a) DOS5 FDISK form diskette and (b) Winblows 98 CD. Start winblows 98 from the CD. If will fail immediately because it will not recognize your hardware but you will end on the promt with access to your CD. Start FDISK from the root of your CD and it is able to to wipe out the partitions with bad MBR info as well.
(2) Start from eCS CD and create a partition for your XP. Make the partition installable and startable so that FDISK will not complain when you quit it. Switch to XP CD, quit FDISK and reboot (by means of ctrl-alt-del, we need a partition with correct MBR info, we are not about to continue installation of eCS).
Now you have a
single partition on your HD prepared for your XP. The fact that the partition is the only one on your HD is important: XP fouls partitions which it was not said to touch. You command XP "install here", and XP will write on other partitions as well

If you have installed something on these partitions, you are losing it. Now, XP cannot do that, there is only one partition on your HD.
(3) Install XP. Tell XP to install on the partition created in (2). Install service packs (I don't know whether you need them but winblows 2003 needed SP3 or so - otherwise, winblows wiped out boot manager or network didn't work).
(4) Back to eCS. Boot from eCS CD. The MBR info is now okay so that you will pass through FDISK. Create a boot manager partition, create a system partition for eCS, install boot manager, add both XP and the eCS partition to the boot manager menu (all this is done from FDISK). Format, install.
(5) Do all partition management from eCS. After having installed, create data partitions both for XP and eCS. Next time you will start XP, format data partitions for XP (seems to be safe). At any rate,
forget XP hard disk manager! Otherwise, you are risking that XP will foul your partitions again!
(6) Now, you have (you should have) boot manager and both XP and eCS in it. Both the operating system and XP should start.