Finally i found a way to install flash player

1.Download the XPI archive of the Flash Player Plugin http://fpdownload.macromedia.com/get/flashplayer/xpi/current/flashplayer-win.xpi to your hard disk. XPI archives are only ZIP files containing the files used by the plugins.
2.Extract the files in the archive
3. Copy the files flashplayer.xpt and NPSWF32.dll to %APPDATA%MozillaPlugins where
%APPDATA% is the folder which holds your applications profiles and settings. (You can open this folder simply choosing "Start → Run → Type in %APPDATA% → OK")
4. Restart Firefox
5. Enjoy your flash websites!

Source :
http://www.varesano.net/blog/fabio/installing+flash+player+plugin+firefox+without+having+administrator+access+or+premissions