http://h10025.www1.hp.com/ewfrf/wc/product?product=3559331&lc=en&cc=us&dlc=en&lang=en&cc=usAlan, let's diagnose;1) Do you have access to a VGA monitor? (CRT style. Looks like a small TV) How about a flat LCD screen monitor with a VGA cable?Need to see if the problem is the graphics chipset, or the Video Cable, or inside the Display Assembly.
http://en.wikipedia.org/wiki/VGA_connectorA) Laptop OFF, monitor OFF, connect the VGA monitor, to the VGA connector on the laptop. (Left side towards the Front)B) Turn the monitor on. If a CRT type allow it to warm up.Turn the laptop on.By default (Factory settings), the display should show on the external VGA monitor.IF not;There are at least 3 display options;1) Internal monitor of laptop ONLY2) Internal monitor of laptop AND external VGA monitor3) External VGA monitor ONLYPress, and hold the Fn key down, (Second key from left on bottom), and at the same time tap once on the F4 key.(The F4 key is the Display Toggle-Over key)Still no display on external VGA monitor?Hold the Fn key down again, and tap once more on the F4 key.Display on external VGA monitor OK? Problem is the video cable, or inside the Display Assembly.Line still on display? Problem is the graphics chipset, or it's mounting to the motherboard. (BGA surface mount)Problem with Video Cable or Inside the Display Assembly:Video Cable; Display Cable when referring to an HP, or Compaq laptop.The Display Cable attaches to the motherboard, under the left side of the Keyboard, and towards the front. It then routes under the left Hinge, and up into the Display Assembly.From there it splits, and connects to the screen Inverter, and back of the LCD screen,
http://www.batterycentury.com/compaq-presario-c700-cable-p-212772.html{ In the photo; On the right side there is a wide connector, (Top), and a small connector, (Bottom)The wide connector connects to the motherboard. The small connector connects to the screen Inverter.The connector to the far left connects to the back of the LCD screen}Just from normal opening, and closing of the laptop, repeatedly, the cable can be pulled on. It can also be pinched in the left Hinge, and be pulled on.This can cause two things:1) Can pull the cable so the connection at the motherboard is loose, or loose at the screen Inverter, or back of the LCD screen. Or all three.I have repaired a few laptops whereby this was the problem. I also have a few users on here, who reported this was the problem.You have to remove the Switch Cover, and partially remove the Keyboard, to access the motherboard side connection, of the Display Cable.You have to remove the Display Assembly, and open it up, to access the LCD screen side connection.You CANNOT just visually inspect the connections, and assume they are plugged in tightly.You need to physically, make sure the connections are plugged in tight.The Switch Cover is just that. A cover. The Keyboard has a Keyboard Cable, that stays attached to the Keyboard, and is connected to the motherboard connector.Therefore, when checking to see if just the motherboard connection is the problem; you can just leave the Keyboard Cable attached to the motherboard, and fire the computer up after physically checking the motherboard connection.{ Flip the Keyboard over, and lay it down on the Palm Rest Cover. Excuse me. Top Cover for HP and Compaq }With the LCD screen, and screen Inverter connections, you can lay the LCD screen down on your 'work' table, and try it. This way you can try it to make sure it is the problem, before reassembling the laptop.Otherwise you will be removing the Display Assembly again, and opening it up, again.[This will all make more sense as you read on ]The Display Cable can also be damaged. Visually check the sheath of the cable. ANY apparent damage, may result in damage to the tiny wires inside the sheath. (Stretched/Broken)Test the wires inside the display cable for continuity. This is done with a multimeter set to OHM's. (1K)If you do not have access to a multimeter, perhaps take it to a 'Mom and Pop' computer store to have it checked. Should only cost a few bucks.Display cable connections are tight/ cable checks out?Problem is the screen Inverter, or LCD screen.The screen Inverter is checked with a Sensitive multimeter. Read fairly expensive,
http://www.fonerbooks.com/test.htmPerhaps the 'Mom and Pop' computer store again.
http://www.batterystyle.com/compaq-presario-c700-inverter-p-261900.html{ A screen Inverter, and an LCD screen are a MATCHED unit. If the Inverter is the problem, make SURE you get the correct one. Same thing with an LCD screen. Make SURE you get the correct one }Screen Inverter checks out? Problem is the LCD screen,
http://www.screentekinc.com/Compaq__Presario__C700_Series-series-laptops-lcd-screens.shtml[ALL of the parts shown are just for examples. NONE are for advertising ]To Add:An LCD screen cannot produce light,
http://solutions.3m.com/wps/portal/3M/en_US/NA_Optical/Systems/BehindTheScenes/Optics101/Click on the monitor icon. (I also would click on -> No thanks)An LCD screen needs an additional light source. A Backlight is the additional light source.A Backlight can be a CCFL, or a series of LED's.(Light Emitting Diode)A CCFL is a Cold Cathode Fluorescent Lamp.Similar to Fluorescent lighting used in homes, and businesses, but on a MUCH smaller scale.Average thickness is 2mm. That is a little larger than 1/16th of an Inch.Average length is almost as long, as the LCD screen is in height.In the next example look at the last 5 photos,
http://www.laptoprepair101.com/laptop/2007/12/09/replace-laptop-backlight-ccfl-lamp/The Compaq Presario C700 series of Notebook PC's uses a single CCFL.A screen Inverter converts the power from the laptop, for the LCD screen, and Backlight.90 PERCENT OF THE TIME, the fault is a bad screen Inverter.This is a link to a free Service Manual from HP Support,
http://h10025.www1.hp.com/ewfrf/wc/manualCategory?cc=us&dlc=en&lang=en&lc=en&product=3559331&In the list click on -HP G7000 Notebook PC and Compaq Presario C700 Notebook PC -Maintenance and Service GuideThis is a PDF file. The computer you are using now has Adobe reader on it, which uses PDF files.After you click on the above file name it may take up to 30 seconds, before the first page comes up.In the Bookmarks menu to the left;1) Click on the + sign to the left of -Removal and replacement procedures2) Click on the + sign to the left of -Component replacement procedures3) Click on one at a time -Switch CoverKeyboardDisplay assemblyPage 58 for the screen Inverter.A) Remove ALL power. Remove the AC adapter (Charger), and BatteryB) De-static yourself before working on the laptop. Perhaps there is a large metal serving plate (Unpainted), you can set on the table, or a large metal knickknack. (Unpainted) Touch before working.C) Use a multi-compartment container, for the various screws you will remove.Label each compartment for the area the screw/s come out of.[If no multi-compartment container is available, you can substitute with a clean egg carton. Label each egg holder ]SOME screws look VERY similar to other screws.Advise do Not mix them up.Need advice along the way post back in a Comment. I'm right here.Regards,joecoolvette