Acer Travelmate 4150

I have a serious problem – my acer laptop doesn’t want to boot. When I turn it on, the fan, HDD and lights seems to be working but the screen stays black and it just freezes. I’ve tried to take out and clean all the parts that can be easliy taken out inc. HDD and RAM but it still doesn’t work. There was no new hardware or software installed recently so I just have no idea what’s wrong. Could anyone help me and send me an email with response to: szymanekk@yahoo.co.uk
I would be very greateful for any help as this is urgent and very important! :/
Many thanks