The Hannspree monitor shows start-up along with my computer monitor,but once it gets on desktop, the Hannspree monitor says "no signal input check video cable", but all the cables are connected property. What should I do?

The computer should beep ONCE when starting-up.
More than one BEEP implies either that the video-card is not responding, or that it is not fully "seated" in its slot.

Try a different video-card in your desktop.

usually points to the resolution settings of the graphics card not matching the monitor resolution settings. Reboot to safe mode on the computer and set the resolution to a lower one. A good starting point would be 1280 x 960 at high res. See if that works

Hello,
I believe the max resolution this LCD can support is 1440 x 900 / 75 Hz. If you set your display resolution higher then that, you will receive the input signal out of range error. Your LDC turns off to protect it self from the invalid settings. If you can not change it back once your PC boots to windows, you may have to do it in save mode by pressing F8 once you power on your PC and before the windows loading screen starts.
Regards, Chris

You ar e getting out of range message because the video signal resolution is too high for the monitor to display, you need to set it to the native resolution of the monitor.

Resolution: http://www.fixya.com/support/r4873371-fixing_out_range_format_not_supported
Resolution adjustment:
From Microsoft: http://www.microsoft.com/resources/documentation/windows/xp/all/proddocs/en-us/display_change_screen_resolution.mspx?mfr=true

and here:
http://www.helpwithpcs.com/tipsandtricks/changing-screen-resolution-win-xp.htm

and here:
http://www.videojug.com/film/how-to-change-screen-resolution-in-windows-xp-and-windoiws-7

With the monitor hooked up, you'll have to use the function key to switch to the VGA output. This is usually the Fn key and the correct F-key. It'll usually have to boxes or something like that. For instance, if your F5 key had 2 boxes on it, hit Fn-F5 and it should start outputting signal to your monitor.

That is computer problem, it shutsdown by itself improperly that is why you see the message on the screen.
When was the last time you blow out all dust inside the PC. You should also try reseating all the cards and memories. Also look for any caps on the mother board with bulging tops.
That will be your starting point.

Basic LCD monitor and TV troubleshooting guide:
http://www.fixya.com/support/r6150077-basic_lcd_monitors_troubleshooting
http://www.fixya.com/support/r5093881-lcd_flat_panel_tv_troubleshooting_guide
http://www.fixya.com/support/r7406380-tv_training_manuals
Failed TV and Monitors: http://s807.photobucket.com/albums/yy352/budm/
Learn about bad caps: http://en.wikipedia.org/wiki/Capacitor_plague

Possible reason is that input signal goes out of range that probably a Screen refresh rate that the monitor cannot handle. Instead of bursting into flames, the monitor shuts itself
down as a protection feature. Look at the monitor manual if you got one.

Safe Mode should allow the monitor to work in the problem account.

Try this.

Boot in Safe Mode (see below)
Switch users to the problem account
Right click the desktop
Select Properties
Click the Settings tab
Click the Advanced button
Click the Monitor tab
Select: Hide modes that this monitor cannot display
Select a different Screen refresh rate
Click Apply twice and then Click OK

Or try this:-
power on the system and press and hold F5.
When a screen appers with some option, try to find a option something realted with VGA setting.
Click that option and let pc start normally.
It will surely work

Can you please get me the make and model of the monitor? Also did you check to see if the refresh rate of the monitor matches with that of the mac mini?

oh no i have same monitor well the only thing i know to do is take it apart and wiggle stuff maybe a culprit will show up if noting then i would just replace on mine the power plug on the back came loose now i cant take out the plug else itll be useless

Hello mcarsten,

Your monitor may not be configured to the correct resolution for the second monitor. If you right click on an empty space on the desktop and then select properties, the display properties will appear. Click on the last tab on the top right. It should be settings or something like that. You should see two boxes with the numbers 1 and 2 in them. Next click on box number 2 and try using the slider below and changing it to different resolutions for your monitor.

Hopefully one of these should work for you.