I'm curious. Are emails stored on a computer's hard drive? What about chat applications that are not downloaded onto your computer, like Meebo? I need to know if I should be worried at work. Thanks for the help!

How are you connected to the internet, etc., at work? If you go through a server, your conversations and E-mails are most likely stored on it, as well as on your own computer.
In any case, it is wise to remember that any communication using your work computer should be considered public, and not private.
Regards,
John