Can someone tell me in which directory path in Windows Firebug is installed?
First, open your profile directory. In Firefox go to Help -> Troubleshooting Information and click Open Containing Folder under Application Basics.
It will be in the extensions folder in a file named firebug@software.joehewitt.com.xpi.
This is basically a ZIP file. The files can easily be extracted after renaming the file extension to .zip.