Correctly handle situation when choice cmd couldn't be found

I have all the choice binaries not working on my XP SP3 machine. *32 says "Cannot run program" and *32_alt and *64 both say "Not a Win32 program". But the script goes on doing useless and potentially harmful stuff. I suggest adding the proper handling as well as providing another binary. I found http://www.dynawell.com/download/ResKit/Microsoft/WinNT/choice.zip working for me (placed it as CHOICE32.EXE according to cmd line syntax it required) but there's also ftp://ftp.microsoft.com/Services/TechNet/samples/PS/Win98/Reskit/SCRPTING/CHOICE.EXE from Win98 that is likely more preferrable (the source is MS) and it worked on my PC too.