Go to ' My Computer '. In menu bar, go to ' Tools>Folder Options '. In new window, go to ' File Types ' tab.
Select your extensions in Registered file types. Hit ' Advanced '. In Edit File Type window, hit ' Change Icon '.
In Change Icon window, you can select your icon. By Browse button, you can explore in more places.
Hit Ok. Hit Ok again. At Last hit Close.
By Registry Editor:
Type ' regedit ' in Run (Press Winkey + R ) to open Registry Editor . Go to ' HKEY_CLASSES_ROOT\(the extension) ' ; for example, ' HKEY_CLASSES_ROOT\.bmp '.
In right part double click on ' (Default) '. In new window check the Value data. Then go to ' HKEY_CLASSES_ROOT\(Value data)\DefaultIcon '; for example ' HKEY_CLASSES_ROOT\Paint.Picture\DefaultIcon '.
In right part double click on ' (Default) ' to modify it. In Value data part, type the path of your Icon or Exe file. At last hit Ok & close Registry Editor .