Implement Chat in ASP.Net 3.5 Web Application

Hi,

I have written below the requirement of my client

"We should also have an option under the contacts tab, for a chat option .The idea behind it is that if a user is looking to communicate with a staff person they should be able to open a chat session and start a typing their questions and/or concerns. While building the chat option, the chats should be logged for certain period of time and there should be an option of retrieving particular chat sessions as needed."

What is the best way to implement this ? I prefer  jquery plugin for implementing the above task () ?  I am using asp.net 2.0.Is there any need to update to 3.5 to achieve the above task ?