Stata Disk And Installed Vista Upgrade Top Xp Disk

I need to replace my wife's motherboard, and I am trying to minimize the amount of change. She is currently running XP, but the hardware is old enough that I cannot simply swap the MBs, because a new board will need a different HAL. I was thinking about installing XP and migrating applications. I was wondering what would happen if I cloned her disk to a SATA disk and installed a Vista upgrade on top of the XP disk. I would run setup and provide the appropriate drivers at the F6 prompt. She has used Vista on occasion when we are out-of-town. I have a separate userID on my laptop that is configured to look as much as possible like XP. The question is whether a Vista upgrade would work on top of an XP image that used a lot of older hardware.