First of all copy a icon file to the root of the drive.
example: c:\icon.ico Then create a file called: autorun.inf in c:\autorun.inf then open that file and type the following: [autorun] icon=icon.ico save and close the file. Now open my computer and refresh.. and woh! icon changed.... you can apply to other drives too. be careful: "autorun.inf" and "ico.ico" must be in the root of the drive. example: c:\autorun.inf and c:\icon.ico. same on the root.