I get this phenomenon with my Wii (Component) and my PC Input (HDMI). I have an Xbox 360 connected via component and the video from it displays just fine. The aspect ratio on the TV is set at "16:9 Standard" which is the setting with zero zoom enabled. I have looked through the TV manual and menus for a solution but I dont see anything. I have also played with the PC and Wii resolution settings and nothing fixes it. Below is a picture I took of the TV as a PC monitor and you can see how the PC image overlaps the screen edges. The Wii does the same thing and overlaps the same distance also. Any suggestions???
I am assuming that the different aspect ratios on your TV besides "16:9 Standard" are not fixing the problem for you and that you have already tried that. I am also assuming that your TV has no controls for adjusting the width/height of the picture. I don't have a solution for the Wii other than to say you might want to put it into 4:3 mode since it doesn't do widescreen natively anyway (I think?). The solution for the PC is easier. Go into the 'control panel' for your video card driver (not Windows control panel) and hope and pray that you have a video card that supports screen scaling. My ATI Radeon 2600 XT uses the Catalyst Control Center (CCC) for this. Good luck. I know it's a pain in the ass. My TV doesn't have height/width adjustments, either.
Most TV's still overscan. Some of the more sophisticated sets can be set for an aspect ratio that provides for zero overscan. Depending on the maker it will be called various things ("dot per dot" proper full pixel mapping). You could also check to see if your vid card can be adjusted to change the overscan/underscan. It should.
I improved my PC issue and solved my Wii issue. Regarding the PC, I have a Nvidia GPU and in its Control Panel, you have to set the options to advanced user. Once this is done, a few more options appear. One of them is to force the GPU to output true HDTV resolutions. After choosing the 1080i equivalent option, my full desktop is now viewable on my TV. There is still a slight overscan but its a major improvement to what I had before and is something I can live with. Regarding the Wii, for some reason when I switch to that input, my TV changes to an aspect ratio of "4:3 Expanded". I just have to change it back to 16:9 Standard and the overscan is fixed. Thanks for the comments and suggestions.