You might also need to fix up the boot partition. I'm not quite sure how to go about this if you're using the vista boot manager, as I've never felt the need to remove vista on my machine
But the process is simply fdisk /mbr from within xp.
http://support.microsoft.com/kb/306559#
No guarantees that this will work properly with vista boot loader. I'd test it first before removing vista. Once you can boot safely into xp, might as well format the vista drive. Transfer all your files over to xp first.
If you break it, the xp recovery disk can fix your mbr, just run the recovery thingy on the installation disk.
Hurray for teh logd!