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Folderico

Allows to change icons of the chosen folder to any chosen by you. And even at connection of a hard disk to other computer of an icon will remain such what they were made by you. You can change an icon of any folder, with any method which is pleasant to you more. Through context menu with preliminary viewing the image. Through dialog, also with preliminary viewing the image. You can choose a icon-theme for context menu. Before installation of version Folderico remove all the previous versions Folderico.

-Download.com

*Does not support Vista

MyFolder Free

Click on a folder with the right button of the mouse and change the folder icon by My Folder. By clicking right button of the mouse on the folder; you can reach all the galleries those defined submenu under Horizon Myfolder Menu. Appearance of the any icons listed can be changed. Changing shape and color of the folders makes easier and faster Windows. Appearance of the folders is up to your choice by My Folder. Customize your computer by My Folder. Resetting and getting back to original icon is possible. Adding new icon and changing the look of the folders are possible. Folder icons can be stored as many as wanted under My Folder gallery section. You can create particular icon library and control the icons by My Folder. Icons defined in My Folder library can be transferred to the galleries in gallery section. My Folder provides adding folders with dll. exe. and icl. extensions to the library. Icon in library can be sent to gallery and used there. Gallaries in My Folder, Colors.Levels, Project Galleries. Easy to use, Accelerates the process. Folder organizing is quicker.

-Developer

*Does not support Vista

In all Windows, you can manually change icons.

Malektips.com describes how to change folder icons in XP:

1. Right-click on a folder and choose "Properties".
2. When the "Properties" multi-tabbed dialog box appears, select "Customize".
3. Click the "Change Icon" button.
4. Choose an icon you wish to use and click "OK", or click "Browse" to browse your system for other icons. Look for .ICO and .EXE files on your system for more icons. You may even want to download some freeware icons over the Internet.
5. Press "OK" to close the dialog box.

Vistax64.com describes how to change the folder icons in Vista:

1. Right click on the folder and click Properties.
2. Click on the Customize tab.
   1. Click on the Change Icon button.
   2. Select a icon and click OK to apply.

OR

1. 1. Click on Browse to choose a icon of your own.
   2. Navigate to where you have the icon saved.
   3. Select the icon and click Open.
   4. Click OK to apply.

As I mentioned above, some good sources for awesome free icons are Dryicons.com, SmashingMagizine.com and Deviantart.com.

Tuneup Utilities 2007

Tuneup Utilites has this feature called "Tuneup Styler". While the skinning, and other goodies only work on Vista, you can use Tuneup Styler to change the icons of folders and such for any Windows. The advantage of Tuneup Styler is that you also get to 'manage' your icons instead of just adding them. You can find icons and skins that you can use with Tuneup Styler mainly at Deviantart.com, but there are other sources. The icons at Dryicons.com and SmashingMagizine.com are also usable.