Try this:
What I'm guessing is that your old monitor ran at a resolution of say 800x600 and you just bought a 15" LCD with a Native resolution of 1024x768.
I'd try the following:
1) Find out what the native resolution of the LCD is and the max refresh rate and then set the video card to those rates. Most people run their monitors at over 75hz BUT most LCD's will have a max refresh rate of 75hz. I'd change the resolution on the video adapter to match up with the LCD and then try again. By the way, you should do all this with your old monitor plugged in.
2) If you don't have your old monitor then I would recommend that you enter windows in safe-mode by holding the cntrl key during boot-up (assuming Win98). Then change the display adapter to a basic VGA adapter and then reboot and re-install the correct drivers for the video card.
Your problem is probably due to the fact that you didn't set the video card up to work with the LCD BEFORE you disconnected the old monitor and so your card is trying to drive your LCD as if it was a monitor. You'll need to connect the monitor and reset the display so that it will work with the LCD.
feel free to email me directly at
nino@purdue.edu