I have a HP G50 laptop which is showing alot of different colour lines. I tried connecting it too a external monitor but am not getting anything on the screen. Is the anyone who knows what the problem may be and how to fix it.
If you are going to use an external monitor, then you need to tell the laptop to output to the external monitor. Don't know which key that is for a HP, but on my Dell it is the Fn+F8 combination.
If you don't see problems on the external monitor, then you know that the laptop's display has a problem. If you still see problems on the external monitor then the video "card" on the laptop is bad.
It's going to be the 'Fn' key and one of the F# keys (likely one that has a monitor icon printed on the key) to turn on the external screen.
I'm pretty certain the LCD itself is bad though, given the description of the problem. LCD's aren't too difficult to replace, just pop off the rubber supports around the screen and you'll find the scews holding the screen together. You might need to do a bit of taking-apart to access the video cable and where it is connected to the mobo, however. You'll also need to detach the backlight and attach it to the new LCD.
New LCD $88.99: http://www.lcdscreen.com/HpSeries_Pavilion_G50__15.4__wxga__1_CCFL.htm
In the off case that the video card is bad, then you'll likely need a new motherboard ($70-$500+) as video cards are usually built-in. If not, then it will be far cheaper to replace ($20-200).