Warlords Battlecry II is not compatible with Windows XP 64-bit.

http://www.gog.com/gamecard/warlords_battlecry_2
Please look at the compatibility notice on the bottom. I would also like to advise anyone reading this thread to always check the system requirements before buying. While we haven't had too many problems with both the 32-bit and 64-bit versions of XP and other flavors of Windows, there are some games that just will not run on a particular variant of a given Windows version. Thankfully, the amount of troublesome games is quite small.