any current Core 2 Duo (or Quad or i7) can do 64 bit computing....
as for amd and processor since the Athlon 64 can also do it too
usually the only problem you should have is the
driver issues...
i really at this point recommend to get more than 4 gb's of ram as x64 os really takes an advantage of this memory....
our resident x64 expert (x64 xPert and goes by the name DiamondNRG as he calls himself) or any admin/mod/7 pro can help you....
as for the issue of OEM's....
ive had included x64 vista in laptop and it was not bad.....
all it need is that a computer has in essence motherboard (that can handled said cpu and x64
drivers) processor (as stated above)