You might have heard rumours of AMD making standard Athlon 64 processors but with 64-bit capabilities disabled on hardware, an yes, it makes little sense to us as it does to you.
Well, The Inquirer has some more information to add to those rumours, it could be that HP has a contract with Intel that keeps them away from using AMD's 64-bit technology. The result from that would be AMD shipping non-64 bit Hammers to HP, although they should still be able to use standard motherboards for the platform.