Here is some more information, im including a Link to the Comments on this information at the bottom. I found them to have some useful information also.
Not only are there going to be several Windows 7 editions, but you will also need to decide if you are going to run a 32 bit or 64 bit version of the operating system. If your CPU is more than a few years old there is a good chance that you can only run the 32 bit version of Windows 7, however if you have a modern processor you may have to decide between each version.
The 32 or 64 bit architecture refers to the memory address length that can be referenced by the processor. This also has an impact on the maximum amount of memory that can be utilised, which is 4GB for a 32 bit CPU (but in reality the maximum accessible ram is often closer to 3.4 GB due to other hardware allocations such as graphics card memory).
Having a 64 bit OS doesn’t automatically make all applications faster because much of today’s software is written and optimised for a 32 bit era. You’ll need software specifically optimised for 64 bit processing to take advantage of any speed improvements. Fortunately, many games are already including such enhancements.
You may think that using a 64 bit OS for a 64 bit processer is an obvious decision, but it is not so straightforward. Introducing a new architecture will cause new compatibility and driver problems that wouldn’t exist under the old 32 bit version.
Pros and Cons of a 64 bit system:
You can address much more than 4GB of memory, which is ideal for avid gamers, CAD, video editors and heavy multi-taskers. However, any 32 bit software you use will still be restricted to 4GB memory – you need a 64 bit CPU, OS and applications to take full advantage of the extra RAM.
16 bit applications will no longer run. Although this is unlikely to be a problem, if you use very old software (from the Windows 3.1 days!) then it will not work under a 64 bit OS.
Existing 32 bit drivers no longer work.If you have older or poorly supported hardware you may find that it can no longer be used. Got a 7 year old scanner that just about works in Vista? You may not be able to get it working in 64 bit Windows 7.
Unsigned kernel-mode drivers no longer work. Along with the issue above, the inability to run unsigned kernel mode drivers will cause problems for old hardware. (There is reportedly a way to bypass this check).
Running some 32 bit applications on a 64 bit OS could actually be slower. The additional overheads in running 32 bit software in 64 bit mode could cause a slight degradation in performance. It will take some time for 64 bit software to become the norm.
The conclusion? Well, it depends on what you use your system for. If you have a 64 bit capable CPU but use older hardware, it would be safe to stay with a 32 bit version for the time being to ensure that you don’t need extra upgrades.
If you’ve got the latest hardware and drivers are available, then it would be worth while taking the step up to a 64 bit OS. If you regularly work with resource hungry applications that are 64 bit optimised (such as video editing, CAD and image packages) then it would be especially beneficial to be able to work with over 4GB of RAM amongst the other improvements.
In the not too distant future, 64 bit computing will be a common standard – as all hardware from the last couple of years has been designed with this in mind. Until a complete upgrade cycle has passed for the majority of users, there is still a strong case for some users to stick with 32 bit Windows for the time being. Once more 64 bit applications start to appear, it would be a good time to make the switch to the new architecture.Comments - Windows 7 Forums
EDIT > Since i am also about to dive into the 64 bit world, i was curious and started looking around and found this:
"You should have AT LEAST 4G of RAM. That's the minimum addressing space for a 64 bit processor running in 64 bit mode. If it doesn't see enough physical RAM to satisfy the need, it will use virtual memory to make up the difference. The end result is constant swapping in and out of the page file and endless hard disk activity."
It sounds like it could be legit, does anyone know for sure, because thats important, IMO.
Edited by s1lents0ul, 24 August 2010 - 08:52 AM.