Not entirely true... Depending on the version of Windows you have, it will only recognize certain amounts of RAM. Win 7 Home Premium I believe tops out at around either 8 or 16GB, then Pro would be around 32GB, and Ultimate/Enterprise is 64GB. Don't quote me on the specific numbers, but there are limits built into the different versions of Windows. So while a 64-bit OS is capable of handling quite a bit more memory, Microsoft introduced artificial limits into Windows 7, and probably the same with Vista. Also, not that it will become an issue for a couple of years at least, but all Intel and AMD 64-bit CPUs using the x86-64 or x64 as it is sometimes colloquially known, are only capable of 48-bit memory addressing. Without getting too far into the weeds, it's a necessary tradeoff to have both 32 and 64-bit process execution. Still, for every additional bit, IIRC, you basically exponentially increase the amount of RAM that can be addressed. So even 48-bit addressing gets well into the TB range.