How can I run another app when pressing the calculator key on my keyboard?
Solution 1:
Did you try Logitech's SetPoint software? It may not let you change what program the key opens, but it's worth a try. I don't have a Logitech keyboard, so I can't check.
You could also try replacing the Calculator executable (%windir%\system32\calc.exe) with the other calculator, but that may be risky.
Solution 2:
Edit this registry key:
HKLM/software/microsoft/windows/currentversion/explorer/appkey/18/ShellExecute
If it does not exist, create a String Value with name ShellExecute and as value the path to your program.