To have multi chat windows on skype is not so challenging, just follow the simple instructions below.
Step 1: Log in your skype account.
Step 2: On the bar menu, choose View -> Split Windows View
After choosing Split Windows View, hoove over any skype account, the chat window will be separated automatically and the main skype interface is only for your skype contact list.
When you don’t want to have multi chat windows, reselect again View -> Single Windows View on the menu bar.