In addition to the (L)user, we've also defined the following:
The  Power Meddler = someone who knows just enough to screw up his/her PC thoroughly, but never admits to having done anything.  The term is derived from "Power User", a more-knowledgable-than-average user.  The Power Meddler may have actually read an article in a  PC magazine...once...maybe...about DOS...  (Formerly classified as a  Magazine reader.)
And also, the A/B-user (pronounced "aay-bee-user") = one who is abusive of the PC, and moreso of the techs who have to bail him out of the hole he dug himself into...
:-)
David