I wouldn't bother with x64 right now. The only place it makes a real difference is if you need more than 4GB of memory, which you won't need on a laptop.
While x64 is stable, there are some incompatibility and driver support issues - some hardware manufacturers aren't even releasing drivers for it since it's not a mainstream OS.
Save yourself some headaches and just get 32-bit XP for now, and wait until Vista for 64-bit.
As far as 32-bit XP goes:
You should use Pro, not Home Edition on your laptop as it has better power management features.