Windows 7 - 32-bit vs 64-bit versions

Microsoft says that 32-bit versions of Windows support up to 4GB of RAM (while 64-bit versions support quite a bit more). While this is technically true, 32-bit versions of Windows are actually limited in their support of RAM because of its underlying architecture. Therefore, even on systems with a full 4GB of RAM, 32-bit versions of Windows can really access only about 3.12GB to 3.5GB of RAM, depending on your configuration. In the initially shipped version of Windows Vista, the System Information window would accurately portray how much RAM it could access, but this confused (and probably infuriated) those who paid for and installed 4GB of RAM, so with Windows Vista Service Pack 1 (SP1), Windows now reports that your PC has 4GB installed, even though it can’t use all of it. Windows 7 carries over this behavior unaltered.

The obvious question is whether you should even bother upgrading to 4GB of RAM when your 32-bit version of Windows 7 can’t actually address almost 1GB of that storage space anyway. The answer is an unqualified yes, for two reasons. First, you’d have to really go out of your way to upgrade a PC to 3GB of RAM instead of 4GB, and the cost differential would be minimal. Second, who says you’re always going to be using a 32-bit version of Windows? You may later decide to go the 64-bit route. When that happens, you’ll be happy you went for the full 4GB of RAM instead of saving a few pennies to no good end.

For the record, we max out the RAM on every single PC we purchase because the costs are so minimal and the effect is extremely positive. You just can’t overstate how important more RAM is to Windows. 8GB of RAM may have been a fantasy a few years ago, but for a modern, Windows 7–based PC, that’s just a starting point.

Source of Information : Wiley Windows 7 Secrets (2009)