XP64 is based on win2k3 server, yes.Some
things can wind up a bit slower - for instance, foxit reader renders a lot slower on XP64 than XP32, for some weird reason (GDI+ problem?). Native x64 applications can
run faster, but don't necessarily; depends on whether they can make use of the extra & wider registers. Memory footprint of applications can
grow somewhat, but it generally isn't very much.
As things are now, 64-bit windows is a bit more resistant against some types of malware.
Basically, I started running XP64 because I didn't need XP32... after getting a new box with 8 gigabytes of memory, I run XP64 because I need it
As for drivers, you might not be able to find it from your laptop vendor, so you need to figure out what hardware you have, and grab drivers from the individual sites of the producers.