1.Copy a icon file to the root of the drive.
Eg: c:\icon.ico

2.Then create a file called 'autorun.inf' in C: Drive.
Open that file and type the following:
___________________

[autorun]
icon=icon.ico
___________________

3.Save and close the file.

The icon will be changed!!!

Note: "autorun.inf" and "ico.ico" must be in the root of the drive. Eg: C:\autorun.inf and C:\icon.ico