As you demonstrate, your file does not contain the same thing as the original command you used. I think it would help to replace ".com" with ".scm".
By the way, to use preformatted text, indent each line with two spaces. Also, you can use asterisks for italics. There's actually an instruction page for this somewhere, but I can't find the link either, so no worries. :-p
Also, I don't mean to burst your bubble, but the main Arc page gives old installation instructions. You don't have to get an old MzScheme version as long as you get arc3.1.tar. http://arclanguage.org/item?id=10254
