Three basic questions about Windows 7.

What is the difference between 32-bit and 64-bit versions of Windows 7?
The terms 32-bit and 64-bit refer to the way a computer's processor (also called a CPU), handles information. The 64-bit version of Windows handles large amounts of random access memory (RAM) more effectively than a 32-bit system. 32-bit computers can only use up to 4GB of memory whereas 64-bit can access in excess of 16GB of memory!

Can I run 32-bit programs on a 64-bit computer?
Most programs designed for the 32-bit version of Windows will work on the 64-bit version of Windows. Notable exceptions are many antivirus programs.
Device drivers (small software programs that help your computer communicate with the device – e.g., printer, scanner, etc.) designed for the 32-bit version of Windows don't work on computers running a 64-bit version of Windows. If you're trying to install a printer or other device that only has 32-bit drivers available, it won't work correctly on a 64-bit version of Windows. To learn how to check for drivers, see Update a driver for hardware that isn't working properly or go to the device manufacturer's website. You can also get information about drivers by going to the Windows 7 Upgrade Advisor webpage.

Which version of Windows 7 should I install: the 32-bit version or the 64-bit version? To install a 64-bit version of Windows 7, you need a CPU that's capable of running a 64-bit version of Windows. The benefits of using a 64-bit operating system are most apparent when you have a large amount of random access memory (RAM) installed on your computer, typically 4 GB of RAM or more. In such cases, because a 64-bit operating system can handle large amounts of memory more efficiently than a 32-bit operating system, a 64-bit system can be more responsive when running several programs at the same time and switching between them frequently. For more information, see Installing and reinstalling Windows 7‍.