well, do you even have an athlon 64? If you want XP to be working in 64-bit, you need XP x64. but the only way for it to work is if you have a 64-bit Pentium or Athlon.
WARNING: A lot of programs designed for Windows XP wont always work on the 64-bit edition. But if you want all of your processor power then you'll have to go with the 64-bit edition
WARNING: A lot of programs designed for Windows XP wont always work on the 64-bit edition. But if you want all of your processor power then you'll have to go with the 64-bit edition