Uhm, try accessing BIOS settings just to see if the hardware is fine.
Just after you turn it on you see white text on the screen, a line of it says what key to press to get into BIOS. It's usually F2 or F12 or Del. press it a few times until you see BIOS options come up instead of the login screen.
If that works, then it's a Win 7 issue, shutdown the laptop and find an install/repair disk and try to restore the system to the nearest restore point following METHOD TWO of this tutorial
. If you don't have an install disk, the first and second steps this tutorial
help you getting one for free.
If the closest restore point is too distant or there are no restore points, use your install/repair DVD/USB flashdrive and follow this tutorial