My dell inspiron 710m has no video but has vertical lines of diferents colors and i can see image perfect thru external monitor

It is the screen, hook your spare monitor back up, press FN key and the F key at top that is assigned, " mine is F5 " there should be a diagram on the F keys to help.

Tryconnecting an external monitor to the laptop. You may have to select the videooutput to display on the external monitor by holding down the blue key and pressing the blue CRT/LCD (located on one of the keys, likeF8,F9, etc..). If the problem occurs on the external monitor with the batteryor AC power, then you have a problem with either the video card or motherboardin the laptop. If the problem does not happen using the external monitor thenyou laptop's LCD display is going bad.

Try connecting an external monitor to the laptop (15 pin VGA connector). If the display appears normal on the external monitor then you have an issue with your laptop's LCD display. If the external monitor also has vertical screens then your video circuit on the laptop has a problem.

Depending on the options you purchased the laptop with, it either has an integrated video circuit into the motherboard or a plug-in video card to the motherboard. If the laptop works fine with external monitor, your motherboard or video card is defective. Your LCD display is probably O.K.

The lines indicate a slow failure of the LCD and it is progressive. The system can be connected to a VGA monitor and you can select the External display using Fn + F8 key combination.
LCDs are about $100 on EBay
http://shop.ebay.com/?_from=R40&_trksid=p3907.m38.l1313&_nkw=Inspiron+2200+LCD&_sacat=See-All-Categories

Vertical lines on half the screen:
Usually the display ribbon cable or the LCD display. At the shop we find out replacing ribbon cable first.
In some rare occasion it can be the display adapter built on the motherboard. You can test the video adapter connecting the laptop to an external display.
regards.

You could have a faulty video card or video cable or connector.
To determine if you have a faulty video card, connect an external monitor to the video port on the laptop, power up the monitor first then boot up the laptop. If you don't get a normal Windows image the the video card is faulty, its part of the motherboard and expensive to replace.
If you get a normal Windows image then the video card is OK and the fault is the LCD screen. Reseat the video cable and or the video connector on the motherboard.
If this doesn't fix your problem then it needs to be serviced.
Have a look at LCD Parts, they have a repair service and DIY info.
Use this link to get to their WEB site.
www.lcdparts.net

i am on a pc at the moment but i think you need to press function key and f5 or f8.

Reseat the video cable connection under the keyboard, and see if the lines go away. If not, connect an external monitor, see if the lines show there. If the lines do not appear on the external monitor, then replace the LCD. If they do appear on the external monitor, replace the motherboard

with the external monitor attached press <FN><F8> to toggle between internal and external display. if still nothing then it sounds like the video card.

MANUAL

Check all the connections (especially the ground screws) that was a problem with one I worked on last year.