How to check if your CPU is 32 or 64 bit?

When trying to install a 64bit app into a 32bit OS, the OS will report your system as being a 32bit system even if your CPU implements 64bit architecture. At this level it is the OS who reports itself as a 32bit, and prevents the execution of a 64 bit app, but there should be no problems executing a 32bit app on a 64bit OS.

But the question is how to really check if the CPU is 64bit or not.
The 64bit compatible CPU includes a “lm” flag (that stands for LONG MODE) that implements the EM64T instruction. This bit is common for both Intel and AMP CPUID.

Anyways, the fastest way to find if the CPU is 32 or 64 (in windows) would be to download the CPU-Z tool, and once you execute it check under the CPU tab, Processor section.
If in the list of supported CPU Instructions, the option EM64T is present, your CPU supports 64bit. 
    

Adrian