To hide information or file behind the image:
-> open any of your drive let us consider D drive ,
-> first copy an image in the D drive and name it as 1 ( right click on the image , click on rename and type 1 and press enter )
-> now open notepad and write ur secret information and save by name 2
-> now copy that notepad in the D drive and compress that notepad ( right click on the file and select 'add to archive' ) ( if u dont hav rar or winzip software ,u must install it )
-> note: these img , rar files are pasted, immediately after opening D drive
->Now open command prompt type the following commands: (after each instruction press enter)
cd\
D:
copy /b 1.jpg + 2.rar 3.jpg

--> a message is show that it is copied !
->NOw in your D drive you will notice a new image with name '3'
->open that image you will see only that image but not ur notepad file
-> How To see your notepad file?
ans: right click on the image '3' -> open with -> choose program -> select winrar or winzip icon and press OK. the zip file is opend and the notepad file can be seen!!!

Also see a demo on this site :[ click here ]