Hi Sarang, here is an aditionnal tip : if you have a F CPU, and the safety functionnality is activated for that CPU, you can still reload the complete program onto the MMC (but it has to be the one that was onto that MMC before, or it has to be a new MMC).
In Simatic Manager (Step7), do ONE left clic on the bloc folder. Then go to Step7 menu 'System cible' and select 'load user program onto the MMC' (sorry but my Step7 is in french version, you must find the appropriate translation ;-)
Just make sure to go to the top menu of Step7 (it's not the same than to do a rigth click on bloc folder, and load the program !)
Tell us if this works
Aditionnal infos : once you have put a 'safe' program onto an MMC, the only way to completely remove it from the MMC is to have a Simatic PG field with Siemens MMC slot, or to have the Siemens MMC programmer, or to use a tool from this post :
http://www.plctalk.net/qanda/showthread.php?t=21758&highlight=siemens+MMC
with this link :
http://personal.telefonica.terra.es/web/suwe/