Change icon in folder is easy, but how if we can change icon in a drive letter?! (C:/, D:/) There's a way.
First choose the icon you want to display it into drive, then save it in drive. Example in C: or in D: partition
Then open notepad and wrote down :
After that, save it as Autorun.inf, Restart your PC...
Hint: to be more secure, Hide the file & set "Read Only"