Why won't my laptop work?

My Laptop Doesn't always boot up when i turn it on. Today i had to turn off and on again about 40 times before it finally loaded up. When i press the power on everything starts working, (internally) but the screen doesn't come on, Other times the screen will come on but it will freeze on the 1st load up screen :( it's an ADVENT 9517. 3-4 years old. Please help me :(