I believe all new Intel chips are 64-bit capable. However, you would need a 64-bit OS to take advantage of that, and that is where the drivers will come in. If you are running a 32-bit OS, just use the 32-bit drivers.
So if you are running XP x64, 2003 x64 or some version of Linux, you'll need 64-bit drivers, otherwise stick with 32-bit.