If everything was working as it should then overscan is supposed to be just that where it pushes a few pixels out of view and underscan should leave you with a border.
 
I personally hate trying to get the picture right on a tv LOL
 
On my tv the pic has always not been quite right size wise and I've never been able to get it right either which has always baffled me.
 
I've always found AMD cards better for tv output myself and thought that would change with HDTV's and over HDMI but alas no.
 
You could try twiddling with scaling but in the end you may just have to make the call between some pixels missing or very slight border (which I think was on the left on mine with the pic pushed out the right LOL)
 
All I can say now for my playback is LONG live DLNA ;)

just turn over scan OFF and the image should crop in the TV screen the right way, you don't need to adjust the setting.
How did you connect your TV into the computer?
I hope you are not using VGA or that is your problem right there, I use HDMI and my 24" HD TV crops the immage correctly using the all surface of the LCD leving no black border or going over hiding part of my screen, it just perfect, and allso try to set the resolution on what ever your NVpannel says "NATIVE" like in my case it is "1920*1080 @60Hz (NATIVE)" and that works fine. 

Phantombadger

Ive turned it on, off, over, under, and auto. if it says 720p its broken. 

what type of connection are you using to connect your computer to the TV?
HDMI, VGA, COMPONENT (3 RCA TYPE = blue, green, red)? 
And what type of video card do you have?

Phantombadger

HDMI.

WOW that is weird, because HDMI should auto crop the image to your screen automatically,  and I think I know what the problem is, is not on the computer it is in your screen setting, ok try this:
 
1) go to your NV controll pannel and select the native screen resolution, if you are a 720p you should set it at 1280*720 @60 or 30Hz what ever your TV supports;
 
2) then click on the left side menu the link "Adjust desktop size and position" on the right side you will see your screen name on top and on the bottom the setting for it, so set on:
2.1)under "scaling" in the bottom "select a scaling mode" set it to "Aspect ratio"
2.2)"performance scaling" set it to "display"
2.3)"Override the scaling mode set by games and programs" deselect it
 
3) now click on "SIZE" and inside the sub menu make sure that you do the fallowing:
3.1)deselect "Enable desktop resizing"
3.2)on the "Select the desktop resize mode reported to the display" select "Auto-select (recommended)"
 
and all that is for make sure that you have the right setting into NV control panel at this point what you have to mess with it's with your TV setting, so the next step you should take is to open your TV setting menu go over to "picture or image" what ever your TV brand put n it and look for "advance video setting" and look for "aspect ratio" and select "WIDE" if you want the image to full up the LCD surface and regarding the image coming up broke or over and hiding part of the screen you have to look for "OVERSCAN" and set it OFF, your TV may have different menu then mine so just mess around with the TV setting after you set the NV panel to what I tell you and that should fix it, now if you get some litle lag on the mouse look into SETTING in your TV and see under VCHIP and set your TV to game mode or VCHIP OFF that should take care of the slow down the VCHIP inside the TV gives you, most TV has this option, my dad samsung TV as it and my 24" INSIGNIA screen does it too.
Good luck
I hope this was help-full