it sounds like your after help in the wrong spot.? but it is the right spot now cause i seen it.
if you are talking about a video card with tv out and it is not working then you should use the proper screen size for the tv on the monitor. and have the tv and the monitor turned on both at the same time that is what i had to do with the properties panel for the display with my ati all in wonder card. it then sent the tv the image from the computer and the computer was sent the images from the tv.
now if you have that set up right then the trouble is that the cable from the tv to the computer might be too long and taking a drain on the signal stregth. if you run it from the tv to the vcr then to the computer that is a drain on it so you might need to add in a 10db 60hrz booster between the tv and vcr if you have the vcr if not just make it closer to the tv then the computer.
that should solve the weak signal. oh you will need to have the software you use for viewing the tv on the computer set to the proper channel mostly 3 if you have cable. but i might be wrong on that number.
if i miss understood your plea for help and answered the wrong way i am sorry.
if you still wish more tech. answers try
www.pcnineoneone.com that is a very fast fourm with a lot of good help there. just sign up for free and start posting.
roving cowboy