No display on screen, but i have sound

You could have a defective screen - a defective inverter or a CCFL lamp.
To determine if you have a LCD screen problem, read this and follow the instructions.

Defective CCFL backlight, it may have the following symptom:

• Screen flashs on red/pink and off.
• Picture stays on in red and slowly be come normal.
• Picture flickering with dim display.
• Picture flickering on and off.

All these symptoms indicate that the LCD backlight lamp (CCFL Lamp) has reached the end of the life and all you need to do is replacing the CCFL lamp

Connect an external monitor to your laptop and power it up, if you see the normal Windows images then the video card and laptop is OK and the problem is definitely the backlight.

Dim image and/or dark display on the laptop's LCD screen indicates a faulty LCD backlight and it could be the inverter that supplies high voltage to the CCFL lamp or it is the CCLF lamp is nearly burnt out or burnt out, most likely this is the case.
The inverter can be replaced easily but the CCLF lamp is more time consuming and requires soldering skills.
Check out www.lcdparts.net for parts, repair service and DIY info.