Desktop.ini a text file that allows you to specify how a file system folder will be viewed. Sometimes one of the shell folders (say, "Pictures") in your system may show a generic yellow colored icon instead of the special icon originally assigned to it. This happens if the Desktop.ini file in that folder is missing or has incorrect entries. This may also occur if the file has lost its read-only or hidden attribute.
For more information on Desktop.ini, see this MSDN article.
Here is a small utility DesktopINIFix that I wrote which fixes the desktop.ini file for various shell folders in Windows Vista.
Fig 1: DesktopINIFix for Windows Vista
Note: After fixing the Desktop.ini, you may have to logoff and login back (or restart explorer.exe shell) for the folder icons to refresh.
About the author
Ramesh Srinivasan founded Winhelponline.com back in 2005. He is passionate about Microsoft technologies and has a vast experience in the ITeS industry — delivering support for Microsoft's consumer products. He has been a Microsoft MVP [2003 to 2012] who contributes to various Windows support forums.