Windows XP 64 is not exactly an upgrade for the current Windows XP and we imagine it will take some time before it is adopted. Even though XP 64 is capable of running most 32 bit applications, you will see little benefit in performance with 32 bit applications and Windows XP 64 is not going to support any 32 bit kernel drivers.
Here is a
link to an interesting review on the performance benefits of XP 64.
http://arstechnica.com/cpu/03q1/x86-64/x86-64-1.html
In order to utilize the capabilities of Windows XP 64 it will require that every hardware driver in the system be ported and modified to support 64 bit operating systems and you will have to find a way to create a 64 bit application. Current software like LabVIEW 7.1 and MSVC 7.1 will not give you a 64 bit applications and therefore you stand to see very little benefit from actually having a 64 bit OS with most of the current development environments. In addition, if your applications doesn't require more than 4GB of memory and you are not doing mathematical computations that are larger than a 32 integer, note the floating point arithmetic is the same for XP and XP 64, you would still see very little benefit from using XP 64 with a 64 bit application and driver.
However, National Instruments is currently investigating Windows XP 64 and it is a good possibility that it will be supported in the future, but there are no current beta drivers available. The speed at which it is supported will be largely dependent on the amount of valid customer requests and the number of customers that will be using Windows XP 64. From what I understand XP 64 is expected to release sometime around the middle of the year, but it will only be an option on some of the larger server and workstations.
If you can, please give me some more information about you application and how you plan to use to develop the application. Why do you feel that you need Windows XP 64 support?
Joshua Prewitt
National Instruments