Hooking up computer to LCD TV

Hello all, My problem is that when I hook up the PC with LCD TV. When I do this I see the bios boot and the windows start bar on the TV just fine. But when it boots up to widows login screen I loose everything as far as a picture goes. I have tried changing the setting on the computer to lower res. But I still have the same problem. Is there something else I could do to resolve this problem? I have tried most of the lower and higher settings on the computer but still nothing works as soon as windows task bar is done. The TV says improper fomat, So I know its getting some kind of signal. When I hook the computer up the the pc mointor things work just fine, and that is where I try to change the res. Then I test it on the tv but no such luck.

Anyone have some kind of input for this problem?

Thanks

^+1, more info would help a lot.

What might be happening is either you are not providing a resolution the TV actually supports or the refresh rate your PC is sending is too high. You might want to make sure refresh rate is set to 54-60Hz and that the resolution is one listed here.

I am hooking up to a LG 42" flat screen. The cable I am using is your standard VGA/SVGA from the computer to the flat screen. The graphics card is built into the motherboard, so I am not sure of the type of the graphic's. The PC is a (Dell Optiplex GX520 SFF Computer 2.5GHz/512/40GB HDD) ( I pluged my laptop into the LG Flat screen just to test to see if it would support drifferent res. Most of the setting from low to high would work from the laptop to the TV. But when I tried to use the same settings from the desktop Dell PC to the LG Flat Screen it would not fuction. Like I stated, when I booted the Dell pc I would see the bios and then the windows start bar running on the Flat Screen, but after that it would go blank. I would then unplug the Flat Screen and plug the Dell into a monitor and try a drifferent setting and replug the Dell to the flat screen with the same results. I am kind of at a loss on what to try next. Thanks for any kind of help you might offer.

That's why a bought a Panasonic Viera Plasma full HD TV. It's the best.