Don't bother reinstalling Windows or changing the OS. That would not fix this issue and would be a major hassle for you.
I would say
Alabalcho is probably right about the cause. However, you may want to first try reinstalling the drivers. Try the following and see if it helps.
NOTE: If you need to type in a password to even get into Windows to do the following, make sure you attached an external keyboard first, to get past the password. Then disconnect the external keyboard and try the following...
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/reconnecting...