How to install:

1. Download a conversation theme
2. Quit digsby
3. Read http://forum.digsby.com/viewtopic.php?id=2879
4. Start digsby and select the conversation theme under Tools - Preferences - Skins!

How to uninstall:

1. Select a different conversation theme in digsby
2. Quit digsby
3. Remove the folder you unzipped (e.g. C:\Documents and Settings\YourName\Application Data\Digsby\MessageStyles\someMessageStyle\ or C:\Program Files\Digsby\res\MessageStyles\someMessageStyle\
4. Start Digsby

Note that some Adium conversation themes won't work with digsby. Just try and see if your favorite works, you shouldn't be able to break anything!