Obtaining IP

Long story short, I need to recover some stuff on a computer that used to be mine but I don't have physical access to. I've got an  admin user and password, and know how to proceed, but I need to find out the computer's IP adress.

I have the current owner's e-mail, though I'm not sure how to proceed.

Ideas please?

If they use HTML email then you could send them a "bug" image, wait for them to read it and check your webserver log.