python Call to external program results in [Error 193] %1 is not a valid Win32 application

Do you have the 64-bit version of Python installed?

I got the same kind of error when I was trying to do a ctype call to a (32-bit) dll running Python 2.7 (64-bit). When I changed to the 32-bit version of Python, the error disappeared and things started working! Perhaps you are having the same problem?

I suppose in Win64, a 64-bit process must be all 64-bit :)

As the warning says, file.wsf isn't an application. It's a script that gets run by being passed as an argument to the script engine. You'll probably need to call the script handler instead. I've no idea what the handler application is, but let's assume that it's cscript.exe. You should adjust your call() to run this and pass the wsf file as a parameter.