Perhaps a "listen to me or I don't fix your computer problems anymore" ultimatum is in order?
Admittedly I've never had any problems getting my family to do as they're told wrt using computers. I think they understand that they do things like I suggest, or they have loads of problems.
Also, I'd remove at least MSNM (and any other messaging apps, as they're evil and full of security holes), as well as OE. Install Firefox and Thunderbird (recent builds).