1. Back up your Interface and WTF folders. After that delete these files from your world of warcraft folder.
2. Download and exctract FFandDB UI in you world of warcraft folder.
3. Open the WTF folder and rename the following :
* ACCOUNTNAME ---> to your account name.
* ServerName ---> to your server name.
* CharacterName ---> to your character name.
4. Load out of date addons in the character selection screen.
5. Load world of warcraft and enjoy!