Is there a program that replaces in a file all hex 20 to 00 automatically?

Pretty much any Hex editor will do that. Just google Hex Editor and you will even find some free ones. ONe that I can think of is at a href="http://download.cnet.com/Hex-Edit-Free/3000-2352_4-10046060.html" rel="nofollow"http://download.cnet.com/Hex-Edit-Free/3…/a