Inspiron 1520 - Screen freezes

Hi,

I have a inspiron 1520 laptop, since a few months ago my screen started to freeze up.

What happens is, I start the laptop and login, after awhile the mouse doesn't respond anymore. All I can do than is restart the laptop by pushing in the power button for a few seconds. The period of freezing will than start early during the Dell logo screen. Which might mean restarting the laptop again. Other times, it can take hours before the screen freezes up.

I am running my laptop on windows vista - 32 bit and I have run memory tests, wireless card test, harddisk test all passed.

I have been searching all over the internet for a solution, but there isn't one. I have no idea what the problem is. I don't have a warranty anymore, so sending it back to Dell won't be financially possible at the moment. Unless it is true that for hardware issues I still have a three years warranty?

I hope one of you can help me out or someone from Dell would be nice.