How can an NSIS installer script discover if the windows OS is 32 or 64 bits?

I need to be able to provide either the 32 or 64 bit version of jspWin.dll with some .jar files based on the windows OS.
The windows batch method is:

Set RegQry=HKLM\Hardware\Description\System\CentralProcessor\0 

REG.exe Query %RegQry% > checkOS.txt

Find /i "x86" < CheckOS.txt > StringCheck.txt

If %ERRORLEVEL% == 0 (

    Echo "This is 32 Bit Operating system"

) ELSE (

    Echo "This is 64 Bit Operating System"

)

according to http://support.microsoft.com/kb/556009

!include "x64.nsh"

...and a simple forum search would have told you that, too.

!include "x64.nsh"

use the ${If} ${RunningX64} to check for x86 or x64.