Connecting a monitor to a different modem

1. Check the power cable: Make sure the power cable is properly connected to the monitor and to the power source.
2. Check the video cable: Make sure the video cable is properly connected to the computer and to the monitor.
3. Check the computer settings: Make sure the computer is set to the correct display settings for the monitor. You can typically do this by right-clicking on the desktop and selecting "Display settings."
4. Check the power source: Make sure the power source is working and that there is no problem with the outlet or power cord.
5. Check the power button: Make sure the power button on the right side of the monitor is not stuck and is functioning properly.
6. Try a different cable or computer: If possible, try connecting the monitor to a different computer or cable to see if the issue is with the computer or cable.

If none of these steps resolve the issue, it may be a problem with the monitor itself

I always start with seeing if when connecting an external monitor to the Laptops VGA output is the same or different to what you see when just via the Laptops screen. Reason is so that can narrow down to JUST Laptop screen or graphics chip, maybe even OR connection at cable either end, Motherboad or Screen.
Is the Laptop turning on alright i.e. no frying, I assume it has dried out from when it got wet. localised to screen only or possibly inside of Laptop....Lights up with power, fan spins hard drive spins, right? If so try an external monitor.

Check that the cable is firmly connected and plugged into the right connection on the computer. Make sure that the monitor is reading from the right input, (i.e. if it's a blue connection it should be set to VGA/Analog, if white then it should be DVI/Digital) or at least set to Automatic.

This can be configured on the monitor by pressing its' Menu button.

Temporarily connect a different monitor to your computer, to see if your video-card is the problem.

Temporarilyh connect your monitor to a different computer (desktop/laptop), to see if your monitor is the problem.

Try a different "data" cable between your monitor and your video-output port.

**Caution. Hazardous voltages inside.
This could be a loose connector inside the monitor connecting the LCD panel. A careful check of these delicate connectors (open, reinsert the cable, close the connector) or remove and reconnect the plugs may fix it. White screen means there is no drive to the LCD panel AT ALL.

How old is this thing? Mine is about 4 or 5 years old... junk it!

Sounds like either  a loose connection or a short in the cable going from the monitor to your computer.  Try disconnecting the monitor from the computer, and plugging it back in again.  If this doesn't resolve the issue, try bending the cable in different places.  If this causes the monitor to correct itself, even just for a little bit, it is a bad cable.  You can take it off from the monitor and the computer, take it to a store that sells cables, and get a new one.  

i have a some problem

You are on the right track. Sometimes the ribbon cables will look fine but the wire inside the insulation is broken and will result in intermittant problems. Definately check the cable first and repair or replace. It is best to meter the cable while not connected to avoid false readings through other components. Should be a relatively easy repair.

make sure the cables are pushed in all the way and tighten. On pick that is out of place can distort color correction. also try reseting the monitor to factory settings.