Hello,
The icons for the My Music and My Pictures (and any Windows XP proprietary folders) are assigned in a special system file, labelled Desktop.ini.
You can't see this file in folders, but it is there...in every folder. To make it visible, you need to go into the specific folder you want to change the icon for, then in exlorer, go to Tools > Folder Options > click the 'View' tab > then check 'Show Hidden Files and Folders' and uncheck 'Hide Protected Operating System Files'
Then, in the specific folder, you should be able to see Desktop.ini. It should open in a text editor (Notepad). The line IconIndex=-237 defines the Icon used from the system's shell32.dll. The following preset system icon values are:
- My Music: IconIndex=-237
- My Pictures: IconIndex=-101
- My Videos: IconIndex=-238
Unfortunately, this method only allows you to change or restore your icons to those available in the system's shell32.dll. Also, there is no index or reference for the specific icons that I know of, so it's either a task of trial and error, or comparing your own folders, or other system's folders.