You can use the following registry location to check if computer is running 32 or 64 bit of Windows Operating System:

 
           HKEY_LOCAL_MACHINE\HARDWARE\DESCRIPTION\System\CentralProcessor\0

 
You will see the following registry entries in the right pane:

  
         Name                     Type                     Data
         ----                     ----                     ----

       Identifier                REG_SZ            x86 Family 6 Model 14 Stepping 12

 
 
The above "x86 Family" indicate that the Operating System version is 32 bit. 

Otherwise (e.g. Intel64 Family) the Operating System version is 64 bit.