If you mean a mouse-over description, then:
- Right-click the folder and select Properties.
- From the Properties dialog box, select the Customize tab, and then click the Change Icon button.
- In the Change Icon dialog box, select an icon from the selections and click OK.
- Click OK to close the Properties dialog box.
- Open the folder, locate the Desktop.ini file, and double-click it.
- Add InfoTip= to the end of the Desktop.ini file.
- Type your detailed description immediately after the = sign.
- Go to File | Save and close Notepad.
You'll see your detailed pop-up description the next time you mouse over that folder.