If you are using 32 bit operating system then a question in your mind arises that why should you upgrade your system to 64 bit. 64 bit operating system is well implemented in windows 7. But before installing windows 7 you should have some specific hardware capacity in your system like at least 1GB RAM and enough space in hard drive. There are two options in windows 7 when you install it either you choose 32 bit or 64 bit. I think x86 is 32 bit while you install.
If you install 4 GB RAM in 32 bit system then it will only show you 2 GB of available ram and remaining RAM is used by the hardware. But 64 bit operating system uses 4 GB RAM and show you right RAM in your system settings.
64 bit system is 15 percent faster than 32 bit system and has higher kernel security. Also it has large data set because it uses 32 x 2 bits and you can install more than 100 GB of RAM in it. 64 bit takes full advantage of your hardware and utilizes it efficiently. Most of the old systems have low ram and processor so it is difficult to upgrade them so it is better that you can buy a new system with the required hardware so that you have good speed and higher privacy. 64 bit systems are ideal for playing heavy games, scientific purpose, graphics software and other high level applications.