victor1 :
Hello,
i changed my windows 7 OS from spanish to english and the function keys stopped working
It sounds like you may have the wrong keyboard selected?
Open Control Panel / Region and Language / Keyboards and Languages tab / Change Keyboards button.
Make sure your Location is set to the country you reside in.
In the Installed Services section, make sure the Keyboard for your location is selected. If you are in the USA, it should show the following:
EN English (United States)
Keyboard
US