Now that Windows 10 is officially out. There are two different CPU versions you can install, 32-bit and 64-bit. (Use the Windows Download Tool here.)
This little tool helps you to determine if your CPU supports 64-bit or not. It’s s released as freeware, 100% free to use.
Download it here: http://www.igorware.com/64bit-checker/download
Link to developer: http://www.igorware.com/64bit-checker/