Note: Before Doing anything Save all your works / Data.
When you turn on your PC you have noticed that icons on the desktop are changed unexpectedly to a blank or missing icon. Don't worry this is because the icon Cache file in the system is got corrupted, you can fix this by rebuilding the Icon Cache file.Just follow the steps mentioned below.
In Windows 7 , 8/8.1/10 Machine you can find a file name called IconCache.db file just delete it and restart your computer and the icon file the IconCache.db file will Rebuild autmatically.