How to determine if your Windows version is 32-bit or 62-bit?

(Windows XP)
Click Start button. Right click My Computer > Properties.
Under System tab, if you see "x64 Edition", your Windows XP version is 64-bit.
Otherwise, you are running 32-bit version.

(Windows 7 or Vista)
Click Start button. Right click My Computer > Properties.
Under System tab, the system type is listed.

What are 32-bit and 64-bit Windows versions?

The way a computer's processor handle information is defined as 32-bit or 64-bit.
64-bit processes a larger amount of RAM better compared to a 32-bit operating system version.

Related topic: How to determine if your Windows version is 32-bit or 62-bit?