After following this tutorial, you will be able to change the default yellow colored folders that appears in left side of explorer pane in Windows 7.
This what the default appearance is:

To change the odd looking yellow monotonous folder icon, you have to follow these steps.
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Click Start button, type œregedit (without the quotation marks) and press Enter from keyboard. Accept the security prompt to run Windows registry editor:

Windows registry editor will open. Go to :
HKEY_LOCAL_MACHINE \ SOFTWARE \ Microsoft \ Windows \ CurrentVersion \ Explorer
Right click on the Explorer key, and select New > then click Key :

Name it as ” Shell Icons ” (without quotation marks).
Now, the important point begins. Right click on the right sided pane and create new string value :

You have to know two things: First the String value (that means what DWORD value you need to create for which folder icon) and the location of icon (that is very easy, just the full path of the icon’s location is needed).
Example:
"3" =" C:\Windows\System32\Shell32,137 "

This will change the closed folders in the Explorer to corresponding icon. Here is a complete list for each value.
0= Unknown file type
1= MSN file types
2= Applications Generic
3= Closed Folder
4= Open Folder
5= 5.25″ Drive
6= 3.25″ Drive
7= Removable Drive
8= Hard Drive
9= NetWork Drive
10= Network Drive Offline
11= CD-ROM Drive
12= RAM Drive
13= Entire Network
14= Network Hub
15= My Computer
16= Printer
17= Network Neighborhood
18= Network Workgroup
19= Start Menu’s Program Folders
20= Start Menu’s Documents
21= Start Menu’s Setting
22= Start Menu’s Find
23= Start Menu’s Help
24= Start Menu’s Run
25= Start Menu’s Suspend
26= Start Menu’s PC Undock
27= Start Menu’s Shutdown 28= Shared
29= Shortcut Arrow
30= (Unknown Overlay)
31= Recycle Bin Empty
32= Recycle Bin Full
33= Dial-up Network
34= DeskTop
35= Control Panel
36= Start Menu’s Programs
37= Printer Folder
38= Fonts Folder
39= Taskbar Icon
40= Audio CD