Shoutbox

You can't merge the contents of the logs, but if you go to the "Messages" tab in Windows Live Messenger options then you can change the folder that logs get put into.

Though it may be an idea to just use the logging capablities of EITHER WLM or Messenger Plus! Live as they both do essentially the same thing (the only differences being that WLM logging enables you to see the previous conversation in the chat window and Messenger Plus! Live logging able to save in .txt format)

You can just cut & paste the existing logs into the same folder to make searching easier