Using of xpcom components in install.js

Hello Everybody,

I am unable to use xpcom object in install.js. Let me explain what I am 
doing here. I am trying to install a bunch of components. For this I am 
using the firefox-installer XPI engine version 1.0.3. Modified the 
config.ini file to match my needs. The first component I install is 
XPCom, followed by Component C1 and C2. Once component C2 is installed, 
I need to change a file from C2 so that it contains the location of C1. 
For this, I am trying to read the file using

var localFile = Components.classes["@mozilla.org/file/local;1"].
		     createInstance(Components.interfaces.nsILocalFile);
localFile.initWithPath(filePath);

But I always get "uncaught exception: Components is not defined". I even 
tried this code as suggested by Dan Veditz after installing XPCom, but I 
still get the same error.

	refreshPlugins(true);

Kindly suggest how to solve this issue.

Thanks,
VM