Its probably because your using the Beta build.. but there is only 1 way i know. take forever, if interested read this:
-----------------------------------------------------------------------------------------------------------------------------------
1 - Right click on File/Folder
2 - Click Properties
3 - Go to the "shortcut tab"
4 - Click " Change Icon
5 - Click the icon you want
6 - click ok..
As i said it would take ages.. but that's the only way i know.