Good news is that the new Calculator works on Windows Vista too, if it’s been ported or migrated to Windows Vista. Windows Vista users who want to use the more advanced Calculator program from Windows 7 can download the following RAR archive which consists of calc.exe with its mui language file extracted from Windows 7 pre-beta build 6801.

To Run Windows 7 Calculator :

1. Simply unpack the content to another folder
2.  Run the calc.exe to use the Windows 7 Calculator in Windows Vista. 

To replace existing default Calculator program in Windows Vista :

1.  Copy calc.exe to \Windows\System32\, and calc.exe.mui (in en-US folder) to \Windows\System32\en-US\ folder
   
   Overwriting existing file (you may want to backup the old Calculator binaries first in case of error running Windows 7 version). Voila, now the new Windows 7 Calculator has been installed on Windows Vista.
   

Download Windows-7-Calculator.rar.