Tags Windows

One way is in Control Panel -> System. Direct link to place in explorer's address bar:

Control Panel\All Control Panel Items\System

There, under "System" you can see a field called "System type" which will say whether the OS is 32-bit or 64-bit.

Another way is to use the command-line interface to WMI. Execute cmd and then:

C:\Users\username>wmic OS get OSArchitecture

As you can see, it shows 64-bit for me.