You will need
- The program CPU-Z
There are many ways to check it. The easiest option does not involve the installation of any additional programs, but at the same time it is not accurate enough. For implementation, just run the task Manager, simultaneously hold down the three keys Ctrl+Alt+Delete in Windows operating system. In the opened window in the Performance tab, in the line "history CPU" available in Windows is the number of cores of the processor of your computer. If there are two or more, you can 99% be sure that the bitness of the processor of this computer is 64 bits as all modern dual core processors - 64-bit.
But the system unit can be quite old and not been updated for a long time, thus a way to find out the bitness of the processor is not suitable. To access additional programs. For more accurate results you'll need at least a couple of these software utilities. The first and simple enough to master - CPU-z Download it from the official website of the program - this little utility is absolutely free and takes very little space on the space of your hard drive. Install it, run it, and in the very first tab called "CPU" displays all the information about your processor. Find the line "Instructions". In it you can see, for example, here such code: MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, ЕМ64ТВКонкретно in your case you are only interested in the acronym "EM64T" - it means that the bit width of the processor - 64-bit. The same means, and "x86-64". Everything else - the processor 32-bit wide.
Another useful program is AIDA64. In contrast to CPU-Z it is paid but has a 30-day trial period. Downloading from the official website by installing and running, go to the tab "mainboard" and then in the item of "CPUID". The line "instruction Sets" will tell you the bitness of the processor is 64 or 32 bits.