if you are trying to modify the original one and just reuse it.. you have to use that one program where you have to edit the different layers.. like 3 of them i believe or so... and then you have to resave it and replace the original ones[im not sure how that program works, but save it in a different directory and reboot it into safemode and copy it into the system32 folder overriding the existing one]... but make sure you made a back up of the original one incase anything happens..
if you are trying to replace it with one alredy made.. you have to reboot in safe mode and override the existing one by replacing it with the new one since windows have the protection