Replying to China yadea,
Your question is rather technical. Please note that the chat history is saved in your computer instead of the server . If you want to re-install your TradeManager,you may first find TradeManager program file in the appointed disk, then find "Users" file, copy and save this file to removable disk or other place in your computer. Then you can re-install your TradeManager, when done please replace the saved "Users" file with the existing one, by doing this, your chat history will be recovered.
Replying to Zhuo,
Copy and paste the "Users" file from one computer to another, it will cover the existing file instead of adding the file to the existing one.