First try discharging all the voilitile memory and static, Unlplug from mains, take out the battery. Now press and hold in the Power On button for at least 30 seconds. Now reassemble switch on and see it if it boots up into W7.
If that doesn't work then try:
Power on or reboot your computer. Press F11 when you see the prompt text on the bottom of of the screen when it gets to the POST screen. (Or simply reboot the machine and keep pressing F11 repeatedly until the Windows 7 system restore process starts and shows you the menu to choose from)
Choose the Non-Destructive System Restore – This recovers the operating system, all programs, and drivers that were installed by default. Any files currently on the computer should not be damaged by this process. (Meaning that you get to keep all of your documents, pictures, videos, etc when using this option.