Originally posted by Vegas
From what I know, 32 and 64 bit architecture have a fair difference between them. 64 bit architecture is mainly more expandable with the latest programs and games out there, and generally run faster on 64 bit CPU's, like a Core 2 Quad, etc.
You can still game on a 32 bit architecture of an Operating System, however running a 64 bit architecture on the appropriate CPU can boost the performance in your computer.
64 bit architecture also allows computers to maximize ram count.
For example, if you had 4GB of ram installed in your computer, and you were running a 32 bit architecture of Windows 7, only 3GB's of that ram can be used, but if you were running a 64 bit architecture, you can use all 4GB's of ram.
If you're deciding on upgrading to a 64 bit operating system, just make sure your system can handle it, it's mainly the CPU you need to worry about.
I hope that answers your question.
Vegas is right. But you don't need to be so careful on what processors you look at. It's becoming increasingly harder and harder to find processors that do not support the 64-bit architecture. I just recently purchased a single core AMD that supports 64-bit, albeit that being counterproductive towards what 64-bit is good at.
Another little fact, aside from breaking the 4gb mark with RAM, is that 64-bit is great for big data projects, such as digital video work, multi-tasking large programs, stress testing and ect. With newer video games, 64-bit is a blessing, your computer can 'make sense' of all the information it's looking for much faster compared to its 32-bit counterpart.
Some cons of 64-bit is that there is software out there that doesn't work with it, or requires tweaking of Windows Settings and registry to get it to work. For example, about a month ago I threw Win7 64-bit on my HTPC, and wanted to listen to some music in the background as I did some miscellaneous work organizing my BluRays, so I downloaded the Pandora Gadget, which to my surprise didn't work. I read up on it a bit, and it had to do with it not being able to recognize that I had the correct Flash Player installed, even though the browser version would work fine.
After changing some stuff in the registry it started to work, but that solution didn't help everyone who had this problem, I suppose I just lucked out.
The ol' standby that I always suggest to people is that, if you want more than 4gb in your PC, than you should use 64-bit. If you have 4gb or less, then just stick to 32-bit to avoid software compatibility problems.