Welcome to the Dell Community @mahmoudelemam1 

Hold down the "D" key, push the power button, release the power button, wait 2-3 seconds and release the "D" key

The laptop should go through an LCD test of solid White, Red, Green, Blue and Black 2 or 3 times.

After completion it should try to automatically boot 2 or 3 times.

Post any results.

Best regards,

U2

I usually assume the simplest things first.

Try the video test offered by U2CAMEB4ME. My guess is that a wire in the video cable bundle is pinched.

I have currently plugged it into the charger The power light is currently off and the charger light is working normally and the light next to the charger is on and off continuously

Tested the white, red, green and blue screen, then tried to boot but it didn't work with the black screen again and the charger light on without being connected to power!

Tested the white, red, green and blue screen, then tried to boot but it didn't work with the black screen again and the charger light on without being connected to power!

OK. So the video test ran OK but still the machine doesn't boot.

When you start it is, press F2 a few times and see if it will go into the BIOS.

• I've already done that but it doesn't go to BIOS. If I press the power button, the fan runs for 15 seconds and then goes off, then the battery indicator, Wi-Fi indicator and Hard drive light are white steadily, except for Hard drive light which turns on and off continuously for 43 seconds and then shut down

Lately I've been experiencing a similar problem with my e7440. Have you tried repeatedly turning it off and on again? For me it randomly works if I try for like 10 mins.

same i was doing this but now it wont turn on 

just showing the light power on

Same issue I am facing during the last 3 days but unable to get satisfied solution on the internet. If you got any solution please mention me, it will be a great favor.