Partition letters Change in Vista and XP dual boot

I have seen many tutorials on dual boot of XP and Vista with Vista already installed. If a computer comes from one of the suppliers like Dell, HP or Gateway, Vista will have a partition D for the Recovery installed. This means you have to use E as the XP parttition. Now here is the strange part of a dual boot from these systems. When you assigned E for XP and install, you are assign H or I for XP. No one addressed this possibility with a dual boot. Once the letters are changed in a volume, Windows will not let you change back to the letters you assigned them to. I have installed a dual boot a few times now never getting the correct partition letters for XP. The last time I tried, Vista and the Recovery letters changed to C for the Recovery and H for Vista. I would love to hear some answers to this problem.

A Little Help
Goose7