OK, so this one didn't happen to me personally..... but....
User: I need to change the screen size
HD: the screen resolution?
User: errr, yeah I htink thats it, needs to 800 or something
HD: no problem, right click on an empty part of the desktop and you should get a menu
User: nothing happened
HD: Strange, OK, try to right click on the My Computer icon?
User: nope still nothing.
HD: ok, just read back to me what you have tried so fat