osfile

/*
 * This is a JavaScript Scratchpad.
 *
 * Enter some JavaScript, then Right Click or choose from the Execute Menu:
 * 1. Run to evaluate the selected text (Ctrl+R),
 * 2. Inspect to bring up an Object Inspector on the result (Ctrl+I), or,
 * 3. Display to insert the result in a comment after the selection. (Ctrl+L)
 */

Components.utils.import("resource://gre/modules/osfile.jsm");

var file = Components.classes["@mozilla.org/file/local;1"]
                     .createInstance(Components.interfaces.nsILocalFile);
file.initWithPath("c:\\Windows\\explorer.exe");

var process = Components.classes["@mozilla.org/process/util;1"]
              .createInstance(Components.interfaces.nsIProcess);

process.init(file);

let args = [OS.Constants.Path.profileDir];
process.run(false, args, args.length);

wouldn't file.reveal() do the job too ?