If the Windows 7 Upgrade Advisor indicates that your PC can support a 64-bit version of Windows, give 64-bit a try.

WindowsSecrets.com > Top Story, July 16, 2009
Some versions of Windows 7 worth it, others not - By Woody Leonhard
http://windowssecrets.com/2009/07/16...rs-not/#story3
If your system uses an Intel Core 2 Duo/AMD Athlon 64 or newer processor, you can run 64-bit. But choosing between 32-bit and 64-bit Windows has more implications than you might think.

Yes, the 64-bit versions of Windows 7 can handle more memory — 32-bit versions top out around 3.4GB. Yes, 64-bit applications frequently run faster than their 32-bit brethren.

But the devil's in the drivers: many manufacturers adamantly refuse to spend the money to create 64-bit drivers for older hardware. After all, they make money by selling new hardware, and 64-bit compatibility doesn't rate very high on the profit-center scorecard.

Fortunately, there's an easy way to tell whether your Vista machine and its peripherals support 64-bit versions of Windows 7. Microsoft's Windows 7 Upgrade Advisor scans your computer and tells you whether Microsoft-approved 64-bit drivers are available for your equipment.