Could also be due to overscan. I suggest calibrating your display with a DVD like Avia or DVE. You can find them on Amazon. You need to calibrate for each input on your diplay: composite, component, svid, DVI and/or HDMI. Granted you need an HDMI/DVI DVD player to handle those.

After calibrating w/ the DVD, you can run this method called "steaming rat", which IMHO, gets you even better results than the DVD alone.

Steaming Rat