Unless he was using DVI, which seems unlikely, the HDMI could help.  But it also sounds like a case of video card resolution not set to monitor resolution, resulting in scaling.  He should make sure that isn't the case.  A 42" is pretty big, is it actually a TV?  My experience has been that TVs act as poor computer monitors, especially for gaming.  But I haven't tried this with a newer TV, so I could now be wrong.