Open the Ease of Access Center panel. You have a or some options related to keyboard that are enabled. Make sure that absolutely every check box are unchecked.
That should fix your problem. You may need to restart.
If your F1 key, on the desktop, shows Windows Help, and doesn't reduce the keyboard brightness, and it a behavior that you want. Do Fn+Caps Lock, this will reverse the keys role, whre now teh keys will do what they are saying, but if you want the F# key, you can just hit Fn+F#.
If the keyboard keys all all wrong, like A does something else, it is probably you switch to Dvorak keyboard, and not QWERTY one (standard keyboard that 99.99% of the people uses). To fix this, open the Language panel (you can find it in the classic control panel), and from there, click on "Options" on the language you use, then click on "Add an input method", and select QWERTY, of your language of your keyboard. Once done, click on "Add", and then remove the existing DVORAK keyboard that should be listed. Once done restart your system, and you should be good.