I have come to the conclusion that XP 64 sucks, excuse the language, there is no other way to put it.
I used to enjoy X64, until after some months, I have begun to notice quite a few strange anomalies.
For instance, both FarCry 64 and UT2004 64 will randomly crash without warning, and so will some other games. Even if my system is absolutely perfect stability wise and in a very good temperature range.
X64 will not shut down correctly and this is a common and well known problem. It used to be able to shut down, then it went to being about a 50% chance of hanging at the shutdown screen and actually shutting down. Now there was a 0% chance of a real shut down. For weeks, I would be forced to do a hard shutdown just to get it off. I have a theory that the lack of proper shutdowns has somehow corrupted the windows installation.
Keep in mind that I had these problems on a machine that would have ZERO problems on XP Pro 32, that had all the latest anti virus and anti spyware, that had ALL the necessary drivers for an X64 installation, that would run Prime 95 for a week straight, that could pass an entire day's worth of running mem test, and that had a cpu load of around 35C.
Also, I cannot see much use for Windows x64 in the future either. By the time there is even halfway decent support for Windows x64, Windows Vista will be out in both 32 and 64 bit flavors, thus eliminating any and all necessity for a 64 bit XP.