Some programs will install extras , there might have been a little check box during installation but those are easy to miss.

The only thing I can think of it that the IM program might have added a tool bar or changed your home page.

It shouldn't have affected the PM sending from here at NT.

If you don't care for the changes you could uninstall the IM program and see if everything goes back the way it was.

Here is a site called meebo - where you can sign on to many IM in one place and no downloads or installing anything.
http://www.meebo.com/

[Any computer, any IM network
Just go to meebo.com to chat with your buddies on every major IM network in a single buddylist. Login with the IM account you already have, there's nothing to download or install, and it's totally free.]
http://www.meebo.com/products/