do any of u guys know of a plugin which will notify u when your contact open a conversation window of u. for example, when i just double-click on my contact but never chat with him, he will be notified. any idea?

There are a few. However they no longer work with the new msn as they give flase notifications. Messenger Discovery x has the feature and so does stuffplug ng beta for msn 7. However these are both betas and the feature does not fully work. It may tell you when someone had changed their display picture

see "CookieRevised's reply to How can you see if someone opens your conversation box"