Try connecting an external keyboard while it is turned off and then turn it on. It should let you use the external keyboard to type it in then. Then, once in Windows, try the following to see if what is up with the attached keyboard.
1. Uninstall the keyboard driver.
2. Reboot the computer (without reinstalling the driver).
3. When it restarts, it should reinstall the driver on its own.
If this doesn't work, you may wish to try connecting an external keyboard and see if it works fine. If it does, then it could be the keys themselves that are the issue.
You may also want to try updating the Synaptics Driver if the above doesn't help.