Try booting in safe mode and see if the keyboard works. Mash F8 after you start the computer, before windows loads. See if the keyboard works in safe mode.
Keyboard drivers are pretty generic. Windows should be loading a generic driver to make the keyboard work. Try booting into BIOS, when your computer starts, mash F1, Return, or Delete, it depends on what computer manufacturer you have. See if the keyboard is working to navigate through BIOS. If THAT doesn't work, I am betting that 1. the keyboard's connection to the motherboard may need to be re-seated, or 2. the keyboard is bad and needs to be replaced. If the keyboard doesn't work there, it is not a driver issue because Windows isn't loaded yet. This is usually a relatively cheap and easy fix.
Hope that helps.