Before you swap out the current motherboard go to device manager and select the IDE ATA/ATAPI Controller and select your current storage controller. Right click, select update driver and select install from a list or specific location. Click don't search I will choose the driver to install and select the standard dual channel IDE controller.
This will prevent the inaccessable boot device blue screen. I have done this multiple times on different platforms with no problems.
Also I found that booting the first time with the new motherboard is best done in the Safe mode where XP will install the drivers it needs and at the same time you can install the new motherboard drivers from its CD.
This saved me doing a repair or a reinstall of XP. My whole system came right up and worked great and very stable.