Difference between 32-bit and 64-bit operating system

There are two main things to keep in mind when choosing between a 32-bit OS and a 64-bit OS: memory support and software compatibility. There are others, of course, but those the two most important.
Typically 32-bit operating systems can only support up to 4 gigabytes of memory, while a 64-bit OS can theoretically support upwards of billions of gigabytes. 64-bit operating systems are limited by artificial software and hardware ceilings, but the ceilings are still much higher than a 32-bit OS. So the short answer for memory support is this: if you want more than 4 gigs of memory, you’ll need a 64-bit OS.

Software compatibility is the other thing to keep in mind, and the more important, in my opinion. Some software that runs on a 32-bit OS will not run on a 64-bit OS, especially older software. Most modern software will run on both 32-bit and 64-bit, but checking your software before you upgrade is the only way to know. A little Googling can usually answer that question for you.

When making your choice, the bottom line is this: if you must have more memory than 4 gigs, go with a 64-bit OS. If you don’t need that much, sticking with a 32-bit OS at this point in the game is a decent choice, if only to ensure that your old software will keep on keepin’ on.