32-bit or 64-bit? Lifehacker.com has a great article on how it all breaks down.

(My default answer: 64-bit! More juice, baby!)

The Lifehacker posts says the following, among other well explained details, in reference to whether you can use your 32-bit apps with your new 64-bit operating system:

Do 32-bit Applications Work on 64-Bit?

The vast majority of your 32-bit applications will continue to work just fine on 64-bit Windows, which includes a compatibility layer called WoW64, which actually switches the processor back and forth between 32-bit and 64-bit modes depending on which thread needs to execute—making 32-bit software run smoothly even in the 64-bit environment.

There are some exceptions to that rule, however: 32-bit device drivers and low-level system applications like Antivirus, shell extensions that plug into Windows, and some media applications simply won’t work without a 64-bit equivalent.

In practice, the vast majority of your favorite applications will either continue to work, or provide a 64-bit version you can use instead—but you should check to make sure.

Very well explained, as is the rest of the post.

In short: with a new computer, there are lots of reasons to go with the 64-bit version of your operating system (especially Windows 7). That being said, there can be compatibility issues with specific applications you regularly use, and you need to check that out first.

Find the article here.