While 64-bit computers are commonplace today, 64-bit operating systems are only just becoming mainstream. Your 32-bit operating system could also be limiting performance if your PC has a 64-bit CPU, which it probably does. A 64-bit operating system offers several key advantages over its 32-bit counterpart. First and foremost is the ability to take advantage of more than 4 GB of memory. A 32-bit operating system is inherently limited to 4,096 MB of memory, meaning after video memory and other peripheral memory, your computer may only be able to use 3 GB of RAM or less. Because of this 4,096 MB limit, files larger than this can take longer to load because they are constantly called from the hard drive instead of the much faster page file memory or RAM. A 64-bit operating system, on the other hand, can boost this limit to 16,000 petabytes (although, in common practice, your software generally limits it to 128 GB).
A 64-bit operating system can also give significant performance increases when running 64-bit versions of software. Some of the largest gains come in very computationally-intensive tasks that deal with high-precision numbers (like 3D rendering and physics simulations). Things like data encryption can run up to five times faster in a 64-bit environment compared to the same system with a 32-bit operating system. You probably don’t do that type of computing, but more popular programs also see performance increases including Photoshop, many compression programs (like 7zip), and video codecs. Even games perform better on a 64-bit system because it gives them access to more than 2 GB of memory and greatly increases stability thanks to the 64-bit operating system’s added precision.
There are also a few downsides to upgrading to a 64-bit operating system. For example, running 32-bit programs in a 64-bit environment can be problematic. Occasionally, 32-bit programs may have trouble running or will not even run at all. Fortunately, this is an issue very rarely experienced now that 64-bit systems have become so mainstream. However, running 32-bit programs on a 64-bit operating system can use a fair bit more RAM, so if you have a computer with just 2 GB or less of RAM, it's probably better for you to stick with a 32-bit operating system.
If you think a 64-bit operating system sounds appealing to you, there’s a way to upgrade both Windows Vista and Windows 7 to 64-bits for free.