Laptop wont run start-up Windows 7

Yesterday My Laptop decided it wasnt going to work even though it had been absoloutly fine the day before.

I switch it on and it loaded the dell logo, then the windows logo. Then it flickerd blue/black and started up the dell logo and the went onto a black screen with the options to "Launch start up repair" or to "start windows normally" i selected to repair it, but it tells me "Start up repair can not repair this computer automatically, i have also tried to do a system restore but that to was unssucsessful. I ran memory diagnostic, which didnt come up with anythhing. and i dont know what else to try!

Does anyone have any idea what may have caused this and if there is a soloution, it is still under warrenty so i will contact dell tomorrow, but thought i might be able to save myself a hefty phone bill, if there is a simple soloution.

Thanks
Dominae