(1) Is grub.conf set up right for this partition table?
Looks good to me.
(2) Is it possible to boot XP at this location, or do I have to
reinstall Linux and XP with their partition reversed, so as to get the
XP partition to a smaller block number?
You wouldn't have to reinstall, but you don't need to.
(3) Is there some quicker way to get the partitions reversed other
than
reinstallation?
You *could* image out the partitions, then back in as you wish. You
don't need to though, mount the windows partition, show us what's in the
root. Also, paste the exact grub error.
Lastly, what was your install order, how did you install windows?
jlc