Checking in Windows 10 or 8
To check what version you’re using on Windows 10 or Windows 8, just open up the old Control Panel and browse down to System and Security -> System (you can also search for System and find it that way).
You’ll immediately see what version you’re using, whether 64-bit or 32-bit.
Checking on Windows 7 or Vista
If you’re using Windows 7 or Windows Vista, all you have to do is pop open your start menu, right-click on the Computer item, and then choose Properties.
Now you’ll see the System information screen—which you might note that you can also get to from Control Panel if you prefer—and down in the system section you’ll see “System type”, which will say 32-bit Operating System or 64-bit Operating System depending on which version you have installed.
Checking on Windows XP
There’s almost no point in checking on Windows XP, because you’re almost positively running a 32-bit version. If you insist, however, you can right-click on My Computer, choose Properties…
And then you’ll see the System Properties window—if you are running a 32-bit version of Windows it won’t say anything here other than Microsoft Windows XP, but if you were running a 64-bit version, it would say that on this window.
What’s the primary difference between the two? You’ll notice that my Windows 7 laptop has 8GB of memory—you’ll need a 64-bit operating system to take advantage of the full amount of memory, since 32-bit Windows can only handle about 4GB.