I have an Compaq Persario SR1000. When switching on it will only display a "No Input signal" on the monitor. I have tried pluging in a separate video card but still get the same message. Any ideas what the problem might be?

I do not know how many Thinkvision models are out there, but here is a site that offers manuals you can read online or download.
This is just a page from the manual I found. Here is a link to the manual I found. http://www.manualslib.com/manual/91948/Lenovo-Thinkvision-E54.html#manual
THIS MONITOR WILL APPEAR TO BE NON-FUNCTIONAL IF
THERE IS NO VIDEO INPUT SIGNAL. IN ORDER FOR THIS
MONITOR TO OPERATE PROPERLY, THERE MUST BE A VIDEO
INPUT SIGNAL.
This feature is designed to conserve electrical energy by reducing power
consumption when there is no video input signal present.when there is no
video input signal present.When there is no video input signal, this monitor,
following a time-out period,will automatically switch to an OFF mode. And the
LED will turn orange. This reduces the monitor's internal power supply
consumption. After the video input signal is restored, full power is restored
and the display is automatically redrawn. The appearance is similar to a
"Screen Saver" feature except the display is completely off. The display is
restored by pressing a key on the keyboard, or clicking the mouse. Lenovo ThinkVision E54 User Manual

If you computer is a desktop meaning it has a computer tower and a separate monitor on it its called a desktop computer and you really need a mouse for it, but if its a laptop/notebook those that are slim and without any tower for it you can use it without any mouse since it has a touch pad that you can use as a replacement for your mouse.

Plug in the VGA cable to the monitor, and to the computer.

The monitor automatically determines which inputs have a valid signal source.

You can also set the monitor's source of video input to VGA, by going to the On Screen Display menu, and the Switch Video Input option.

Here is the User Manual,

http://h10032.www1.hp.com/ctg/Manual/c00834092.pdf

If you have questions post in a Comment.
We'll step by step you through it.

Regards,
joecoolvette

Unplug all the Cables from Compaq Presario 5103 CL and leave the Keyboard, mouse and monitor cable pluged in.

Now make sure the power cable of the monitor should be pluged in and the power cable of the tower should be pluged in.

Now to check if the montor is fine just unplug the video cable only which will show no input signal on the screen. If it shows this signal the monitor is fine. Plug back in the video cable.

If the monitor is going to sleep mode it might be possible that the old computer ( Compaq Presario 5103 CL ) is in stand by mode. hit any key on the keyboard and it should come back .

If it is not in the stand by mode then do one thing. Check the same monitor with the new computer. If it is working. Perfect ..!

Do one thing now ..!

Unplug all the cables from your old system and then press the power button for 30 sec and let it go. Now plug the keyboard, mouse and the monitor try again.
If it works Perfect. If not ..!

Then you need to open the tower and check on the processor FAN is it running..? If its not running you will not get the display as the fan is responsible for the display on the screen. Otherwise...!

Check the Tower possibly the Tower is not getting the power.

Try these steps and let me know If it works

Bring up the monitor menu. There should be a button on the monitor itself. Find the signal input, change from analog to digital (DVI-D). That should take care of it.

Everything seems perfectly normal...

When you connect the computer to the monitor via an analog VGA cable, you get signal on the analog input.
When you connect them via a DVI cable, you feed the monitor's DIGITAL input, so the monitor doesn't get any signal on it's analog input, and informs you about it.
You have to select the digital input from the monitor's On Screen Menu, and then start the computer up - you should see the picture OK.
Also remember to set the display resolution on your computer to match the optimum (native) resolution of your monitor - this will give you optimum picture quality. In case of VA712B it will be 1280x1024.
Good luck and please come back with a testimonial if helped.

have you tried going to menu and setting back to factory defaults? also, disconnect power cable and leave unplugged for 1 minute. Plug back in then see if problem is still there. Otherwise, something is wrong with the monitor that will need serviced or exchanged.

if another monitor is available check it on your system and check yours on another. this is the simplest way to eliminate possibilities. could be your video card all together, just not kicking out a signal

Unless compaq displays that message when the computer goes into sleep mode, it could be a virus.

I have been having the same problem with my hpvs17 monitor when i start to use my web browser on linux distros. Now, for the next few days i am going to try my system on a regular crt monitor. if the monitor does not crash, than i will have to say that the hpvs17 monitor has a defect.It seems that when i go online, while i am in the middle of searching something, the monitor just shuts off and i get "input signal out of range".