File, Folder or Shortcut Icons:
1. Right click on the item to change and select properties
2. Click on the shortcut tab and click the "Change Icon..." button
3. Select or navigate to your icon of choice and hit enter
These are pretty simple steps and best of all free. You might run into some difficulty changing certain icons when going this route and so some software based help might be in order...Microangelo On Display: This is is the only Windows 7 compatible icon changing software out there at the moment but it does the job so there really isn't a need for much else. Unfortunately the software does not allow batch customization however it does allow for changing pretty much every icon. By adding a dialog field when you right click on an item, Microangelo more or less integrates into Windows, so while it may be missing some bells it takes care of the whistles. It isn't freeware, but at $24.95 it won't break the bank.
Now that you know how to change those stock icons, check out the first link below to get some sweet new desktop candy!
Other icon related links: