How about a 64-bit operating system with that 64-bit processor?
All PCs now ship with Intel or Advanced Micro Devices 64-bit processors. Until recently, however, most consumer laptops have come with a 32-bit version of Vista. There are many reasons for this, two of the biggest being a lack of driver support and the larger memory requirements for the 64-bit OS.
But memory is no longer an issue. Many of the new sub-$1,000 laptops at Best Buy, for example, now come with 4GB of memory standard. Out of the 11 HP laptops listed as "new arrivals" at Best Buy, 9 come with 4GB of memory and 64-bit Vista. Ironically, the other two new-arrival HP systems come with "Windows Vista Business downgraded to XP Pro."
In other words, you get either XP or 64-bit Vista: 32-bit Vista is not offered standard at all in this list of new arrivals.
What's the difference between 32- and 64-bit Vista? Here's what Microsoft says: "The 64-bit versions of Windows can utilize more memory than 32-bit versions of Windows. This helps minimize the time spent swapping processes in and out of memory by storing more of those processes in random access memory (RAM) rather than on the hard disk. This, in turn, can increase overall program performance."
One potential problem is driver confusion. Some buyers of retail laptops may not be aware that they are getting a 64-bit OS that requires 64-bit drivers. HP, for its part, provides plenty of 64-bit drivers. For the HP Pavilion dv5t laptop, drivers include those for the Nvidia GeForce 9200M and GS/9600M GT graphics chips, as well as those for the Mobile Intel 4 Series Express chipset family. Keyboard, mouse, network, and storage drivers--among others--for 64-bit Vista are also listed.
Also, Microsoft publishes software compatibility lists at its Windows Vista Compatibility Center. Though photo-editing applications such as Adobe Photoshop and CorelDRAW are listed as compatible, many applications are listed as not compatible or "unknown." In particular, a number of games are tagged as "status unknown" or "not compatible." Popular games, such as Crysis and World of Conflict are compatible, however.
One other thing to keep in mind: older "legacy" hardware could be a problem on 64-bit Vista. Although many older devices have 32-bit Vista drivers, that's not necessarily the case for the 64-bit version.