Its not booting but installing Windows from the HP branded Windows disc that could potentially be a problem if the Windows disc is BIOS locked. Otherwise, XP will just reset the activation when it detects a new/different motherboard, which will need to be re-activated within 3 days.
The OEM EULA allows the user to apply his Windows license obtained with a prebuilt OEM system to a new motherboard so long as the reason for replacing the motherboard is due to failure or defect, but not if a working motherboard is 'upgraded' to obtain new features, function, or capability.
When re-activating Windows, you'll have to call Microsoft and do the installation ID thing. When asked the reason for re-activating, say that your motherboard died and had to be replaced.
The HP P4SD-LA (Stingray) is standard Micro-ATX form factor based on Intel 865G (848P for Oxford). Any standard Micro-ATX motherboard should fit just fine, but the I/O backplane shield may need to be replaced (or removed). Also, you won't easily find a non-OEM motherboard that features the same card reader connector because it is only used by large OEMs. Some Intel OEM boards have this connector, though I don't know if it is compatible with your card reader. You may need to ditch your card reader in favor of one that uses standard USB header (internal) or USB port (external).
If you get a motherboard that uses an Intel chipset, you should have little problem swapping without having to re-install Windows. Just boot into Safe Mode by invoking the boot menu (pressing F8 IIRC) the first time you boot the PC with the new motherboard and give Windows a few minutes to load. After a while, it will usually say 'your new hardware is installed' and prompt you to restart. The second time you can boot normally into Windows. If you use a USB mouse and keyboard, I recommend that you find a PS/2 mouse or keyboard because USB devices may not work until Windows finishes installing them on the next restart.
If the new motherboard chipset is based on any flavors of the new 9xx family from Intel, you may want to download the latest chipset INF utility from Intel and install it after the first restart to update support for the newer core logic.